Merge branch 'cancellable-initializer'

22 files changed, 531 insertions, 444 deletions

diff --git a/ios/MullvadREST/RESTAccessTokenManager.swift b/ios/MullvadREST/RESTAccessTokenManager.swift
index d8d7ef5521..8b374b88d5 100644
--- a/ios/MullvadREST/RESTAccessTokenManager.swift
+++ b/ios/MullvadREST/RESTAccessTokenManager.swift
@@ -27,42 +27,34 @@ extension REST {
             accountNumber: String,
             completionHandler: @escaping (Result<REST.AccessTokenData, Swift.Error>) -> Void
         ) -> Cancellable {
-            let operation = ResultBlockOperation<REST.AccessTokenData>(dispatchQueue: dispatchQueue)
+            let operation =
+                ResultBlockOperation<REST.AccessTokenData>(dispatchQueue: dispatchQueue) { finish -> Cancellable in
+                    if let tokenData = self.tokens[accountNumber], tokenData.expiry > Date() {
+                        finish(.success(tokenData))
+                        return AnyCancellable()
+                    }
 
-            operation.setExecutionBlock { operation in
-                if let tokenData = self.tokens[accountNumber], tokenData.expiry > Date() {
-                    operation.finish(result: .success(tokenData))
-                    return
-                }
+                    return self.proxy.getAccessToken(accountNumber: accountNumber, retryStrategy: .noRetry) { result in
+                        self.dispatchQueue.async {
+                            switch result {
+                            case let .success(tokenData):
+                                self.tokens[accountNumber] = tokenData
 
-                let task = self.proxy.getAccessToken(
-                    accountNumber: accountNumber,
-                    retryStrategy: .noRetry
-                ) { result in
-                    self.dispatchQueue.async {
-                        switch result {
-                        case let .success(tokenData):
-                            self.tokens[accountNumber] = tokenData
+                            case let .failure(error) where !error.isOperationCancellationError:
+                                self.logger.error(
+                                    error: error,
+                                    message: "Failed to fetch access token."
+                                )
 
-                        case let .failure(error) where !error.isOperationCancellationError:
-                            self.logger.error(
-                                error: error,
-                                message: "Failed to fetch access token."
-                            )
+                            default:
+                                break
+                            }
 
-                        default:
-                            break
+                            finish(result)
                         }
-
-                        operation.finish(result: result)
                     }
                 }
 
-                operation.addCancellationBlock {
-                    task.cancel()
-                }
-            }
-
             operation.completionQueue = .main
             operation.completionHandler = completionHandler
 
diff --git a/ios/MullvadTypes/Cancellable.swift b/ios/MullvadTypes/Cancellable.swift
index a00b76eeda..8f658a6da1 100644
--- a/ios/MullvadTypes/Cancellable.swift
+++ b/ios/MullvadTypes/Cancellable.swift
@@ -13,3 +13,22 @@ public protocol Cancellable {
 }
 
 extension Operation: Cancellable {}
+
+/// An object representing a cancellation token.
+public final class AnyCancellable: Cancellable {
+    private let block: (() -> Void)?
+
+    /// Create cancellation token with block handler.
+    public init(block: @escaping () -> Void) {
+        self.block = block
+    }
+
+    /// Create empty cancellation token.
+    public init() {
+        block = nil
+    }
+
+    public func cancel() {
+        block?()
+    }
+}
diff --git a/ios/MullvadVPN/Extensions/Result+Extensions.swift b/ios/MullvadTypes/Result+Extensions.swift
index 204df0714e..a471d9ab26 100644
--- a/ios/MullvadVPN/Extensions/Result+Extensions.swift
+++ b/ios/MullvadTypes/Result+Extensions.swift
@@ -9,7 +9,7 @@
 import Foundation
 
 extension Result {
-    var value: Success? {
+    public var value: Success? {
         switch self {
         case let .success(value):
             return value
@@ -18,7 +18,7 @@ extension Result {
         }
     }
 
-    var error: Failure? {
+    public var error: Failure? {
         switch self {
         case .success:
             return nil
@@ -27,7 +27,7 @@ extension Result {
         }
     }
 
-    var isSuccess: Bool {
+    public var isSuccess: Bool {
         switch self {
         case .success:
             return true
@@ -36,7 +36,7 @@ extension Result {
         }
     }
 
-    func tryMap<NewSuccess>(_ body: (Success) throws -> NewSuccess) -> Result<NewSuccess, Error> {
+    public func tryMap<NewSuccess>(_ body: (Success) throws -> NewSuccess) -> Result<NewSuccess, Error> {
         return Result<NewSuccess, Error> {
             let value = try self.get()
 
@@ -44,7 +44,7 @@ extension Result {
         }
     }
 
-    @discardableResult func inspectError(_ body: (Failure) -> Void) -> Self {
+    @discardableResult public func inspectError(_ body: (Failure) -> Void) -> Self {
         if case let .failure(error) = self {
             body(error)
         }
@@ -53,7 +53,7 @@ extension Result {
 }
 
 extension Result {
-    func flattenValue<T>() -> T? where Success == T? {
+    public func flattenValue<T>() -> T? where Success == T? {
         switch self {
         case let .success(optional):
             return optional.flatMap { $0 }
diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index d12da06daa..2dbb51e2b2 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -26,7 +26,6 @@
 		06410E05292D0FC000AFC18C /* SettingsParser.swift in Sources */ = {isa = PBXBuildFile; fileRef = 06410E03292D0F7100AFC18C /* SettingsParser.swift */; };
 		06410E07292D108E00AFC18C /* SettingsStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = 06410E06292D108E00AFC18C /* SettingsStore.swift */; };
 		06410E08292D117800AFC18C /* SettingsStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = 06410E06292D108E00AFC18C /* SettingsStore.swift */; };
-		06410E09292D990C00AFC18C /* Result+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F1311427E0B2AB007AC5BC /* Result+Extensions.swift */; };
 		06799ACE28F98E1D00ACD94E /* MullvadREST.h in Headers */ = {isa = PBXBuildFile; fileRef = 06799ABE28F98E1D00ACD94E /* MullvadREST.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		06799AD128F98E1D00ACD94E /* MullvadREST.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 06799ABC28F98E1D00ACD94E /* MullvadREST.framework */; };
 		06799AD228F98E1D00ACD94E /* MullvadREST.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = 06799ABC28F98E1D00ACD94E /* MullvadREST.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
@@ -117,7 +116,6 @@
 		585E820327F3285E00939F0E /* SendStoreReceiptOperation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 585E820227F3285E00939F0E /* SendStoreReceiptOperation.swift */; };
 		58607A4D2947287800BC467D /* AccountExpiryInAppNotificationProvider.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58607A4C2947287800BC467D /* AccountExpiryInAppNotificationProvider.swift */; };
 		586168692976F6BD00EF8598 /* DisplayError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 586168682976F6BD00EF8598 /* DisplayError.swift */; };
-		586250BB29E6F8F300F4B521 /* OperationCancellationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 586250BA29E6F8F300F4B521 /* OperationCancellationTests.swift */; };
 		5862805422428EF100F5A6E1 /* TranslucentButtonBlurView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5862805322428EF100F5A6E1 /* TranslucentButtonBlurView.swift */; };
 		5864211F29F04CED00822139 /* UIBarButtonItem+Blocks.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5864211E29F04CED00822139 /* UIBarButtonItem+Blocks.swift */; };
 		5864859929A0D028006C5743 /* FormsheetPresentationController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5864859829A0D028006C5743 /* FormsheetPresentationController.swift */; };
@@ -222,6 +220,9 @@
 		58ACF64B26553C3F00ACE4B7 /* SettingsSwitchCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58ACF64A26553C3F00ACE4B7 /* SettingsSwitchCell.swift */; };
 		58ACF64D26567A5000ACE4B7 /* CustomSwitch.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58ACF64C26567A4F00ACE4B7 /* CustomSwitch.swift */; };
 		58ACF64F26567A7100ACE4B7 /* CustomSwitchContainer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58ACF64E26567A7100ACE4B7 /* CustomSwitchContainer.swift */; };
+		58AFC99529F96F7B000829DE /* AsyncBlockOperationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58AFC99429F96F7B000829DE /* AsyncBlockOperationTests.swift */; };
+		58AFC99729F9753D000829DE /* AsyncResultBlockOperationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58AFC99629F9753D000829DE /* AsyncResultBlockOperationTests.swift */; };
+		58AFC99929F97856000829DE /* TransformOperationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58AFC99829F97856000829DE /* TransformOperationTests.swift */; };
 		58B0A2A8238EE68200BC001D /* RelaySelectorTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 584B26F3237434D00073B10E /* RelaySelectorTests.swift */; };
 		58B26E1E2943514300D5980C /* InAppNotificationDescriptor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58B26E1D2943514300D5980C /* InAppNotificationDescriptor.swift */; };
 		58B26E22294351EA00D5980C /* InAppNotificationProvider.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58B26E21294351EA00D5980C /* InAppNotificationProvider.swift */; };
@@ -335,13 +336,13 @@
 		58E11188292FA11F009FCA84 /* SettingsMigrationUIHandler.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E11187292FA11F009FCA84 /* SettingsMigrationUIHandler.swift */; };
 		58E20771274672CA00DE5D77 /* LaunchViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E20770274672CA00DE5D77 /* LaunchViewController.swift */; };
 		58E25F812837BBBB002CFB2C /* SceneDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E25F802837BBBB002CFB2C /* SceneDelegate.swift */; };
+		58E45A5729F12C5100281ECF /* Result+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F1311427E0B2AB007AC5BC /* Result+Extensions.swift */; };
 		58E511E628DDDEAC00B0BCDE /* CodingErrors+CustomErrorDescription.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E511E528DDDEAC00B0BCDE /* CodingErrors+CustomErrorDescription.swift */; };
 		58E511E828DDDF2400B0BCDE /* CodingErrors+CustomErrorDescription.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58E511E528DDDEAC00B0BCDE /* CodingErrors+CustomErrorDescription.swift */; };
 		58EE2E3A272FF814003BFF93 /* SettingsDataSource.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58EE2E38272FF814003BFF93 /* SettingsDataSource.swift */; };
 		58EE2E3B272FF814003BFF93 /* SettingsDataSourceDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58EE2E39272FF814003BFF93 /* SettingsDataSourceDelegate.swift */; };
 		58EF580B25D69D7A00AEBA94 /* ProblemReportSubmissionOverlayView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58EF580A25D69D7A00AEBA94 /* ProblemReportSubmissionOverlayView.swift */; };
 		58EF581125D69DB400AEBA94 /* StatusImageView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58EF581025D69DB400AEBA94 /* StatusImageView.swift */; };
-		58F1311527E0B2AB007AC5BC /* Result+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F1311427E0B2AB007AC5BC /* Result+Extensions.swift */; };
 		58F185AA298A3E3E00075977 /* TunnelCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F185A9298A3E3E00075977 /* TunnelCoordinator.swift */; };
 		58F19E35228C15BA00C7710B /* SpinnerActivityIndicatorView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F19E34228C15BA00C7710B /* SpinnerActivityIndicatorView.swift */; };
 		58F2E144276A13F300A79513 /* StartTunnelOperation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F2E143276A13F300A79513 /* StartTunnelOperation.swift */; };
@@ -556,6 +557,13 @@
 			remoteGlobalIDString = 5898D28829017BD300EB5EBA;
 			remoteInfo = TunnelProviderMessaging;
 		};
+		58EED36D29FBEF040000CBAF /* PBXContainerItemProxy */ = {
+			isa = PBXContainerItemProxy;
+			containerPortal = 58CE5E58224146200008646E /* Project object */;
+			proxyType = 1;
+			remoteGlobalIDString = 58D223D4294C8E5E0029F5F8;
+			remoteInfo = MullvadTypes;
+		};
 		58FBDAA122A52A6800EB69A3 /* PBXContainerItemProxy */ = {
 			isa = PBXContainerItemProxy;
 			containerPortal = 58CE5E58224146200008646E /* Project object */;
@@ -749,7 +757,6 @@
 		585E820227F3285E00939F0E /* SendStoreReceiptOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SendStoreReceiptOperation.swift; sourceTree = "<group>"; };
 		58607A4C2947287800BC467D /* AccountExpiryInAppNotificationProvider.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccountExpiryInAppNotificationProvider.swift; sourceTree = "<group>"; };
 		586168682976F6BD00EF8598 /* DisplayError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DisplayError.swift; sourceTree = "<group>"; };
-		586250BA29E6F8F300F4B521 /* OperationCancellationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OperationCancellationTests.swift; sourceTree = "<group>"; };
 		5862805322428EF100F5A6E1 /* TranslucentButtonBlurView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TranslucentButtonBlurView.swift; sourceTree = "<group>"; };
 		5864211E29F04CED00822139 /* UIBarButtonItem+Blocks.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "UIBarButtonItem+Blocks.swift"; sourceTree = "<group>"; };
 		5864859829A0D028006C5743 /* FormsheetPresentationController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FormsheetPresentationController.swift; sourceTree = "<group>"; };
@@ -852,6 +859,9 @@
 		58ACF64C26567A4F00ACE4B7 /* CustomSwitch.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CustomSwitch.swift; sourceTree = "<group>"; };
 		58ACF64E26567A7100ACE4B7 /* CustomSwitchContainer.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CustomSwitchContainer.swift; sourceTree = "<group>"; };
 		58AEEF642344A36000C9BBD5 /* KeychainError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = KeychainError.swift; sourceTree = "<group>"; };
+		58AFC99429F96F7B000829DE /* AsyncBlockOperationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AsyncBlockOperationTests.swift; sourceTree = "<group>"; };
+		58AFC99629F9753D000829DE /* AsyncResultBlockOperationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AsyncResultBlockOperationTests.swift; sourceTree = "<group>"; };
+		58AFC99829F97856000829DE /* TransformOperationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TransformOperationTests.swift; sourceTree = "<group>"; };
 		58B0A2A0238EE67E00BC001D /* MullvadVPNTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = MullvadVPNTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		58B0A2A4238EE67E00BC001D /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		58B26E1D2943514300D5980C /* InAppNotificationDescriptor.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InAppNotificationDescriptor.swift; sourceTree = "<group>"; };
@@ -1201,6 +1211,7 @@
 				58900D0228BBDCC70094E4F0 /* FixedWidthInteger+Arithmetics.swift */,
 				06410E172934F43B00AFC18C /* PacketTunnelErrorWrapper.swift */,
 				58CAFA01298530DC00BE19F7 /* Promise.swift */,
+				58F1311427E0B2AB007AC5BC /* Result+Extensions.swift */,
 				58D223D7294C8E5E0029F5F8 /* MullvadTypes.h */,
 			);
 			path = MullvadTypes;
@@ -1432,7 +1443,6 @@
 				5871FB9F254C26BF0051A0A4 /* NSRegularExpression+IPAddress.swift */,
 				06FAE67828F83CA50033DD93 /* RESTCreateApplePaymentResponse+Localization.swift */,
 				58B9EB142489139B00095626 /* RESTError+Display.swift */,
-				58F1311427E0B2AB007AC5BC /* Result+Extensions.swift */,
 				58A8EE592976BFBB009C0F8D /* SKError+Localized.swift */,
 				58FD5BEF24238EB300112C88 /* SKProduct+Formatting.swift */,
 				58A8EE5D2976DB00009C0F8D /* StorePaymentManagerError+Display.swift */,
@@ -1643,11 +1653,13 @@
 		589A455328E094B300565204 /* OperationsTests */ = {
 			isa = PBXGroup;
 			children = (
-				58DF5B7E2852778600E92647 /* OperationSmokeTests.swift */,
+				58AFC99429F96F7B000829DE /* AsyncBlockOperationTests.swift */,
+				58AFC99629F9753D000829DE /* AsyncResultBlockOperationTests.swift */,
+				580CBFB72848D503007878F0 /* OperationConditionTests.swift */,
 				58DF5B772852178600E92647 /* OperationInputInjectionTests.swift */,
 				583E1E292848DF67004838B3 /* OperationObserverTests.swift */,
-				580CBFB72848D503007878F0 /* OperationConditionTests.swift */,
-				586250BA29E6F8F300F4B521 /* OperationCancellationTests.swift */,
+				58DF5B7E2852778600E92647 /* OperationSmokeTests.swift */,
+				58AFC99829F97856000829DE /* TransformOperationTests.swift */,
 			);
 			path = OperationsTests;
 			sourceTree = "<group>";
@@ -2198,6 +2210,7 @@
 			buildRules = (
 			);
 			dependencies = (
+				58EED36E29FBEF040000CBAF /* PBXTargetDependency */,
 			);
 			name = Operations;
 			productName = Operations;
@@ -2568,9 +2581,11 @@
 			files = (
 				589A455F28E094BF00565204 /* OperationConditionTests.swift in Sources */,
 				589A455E28E094BF00565204 /* OperationInputInjectionTests.swift in Sources */,
-				586250BB29E6F8F300F4B521 /* OperationCancellationTests.swift in Sources */,
+				58AFC99529F96F7B000829DE /* AsyncBlockOperationTests.swift in Sources */,
+				58AFC99729F9753D000829DE /* AsyncResultBlockOperationTests.swift in Sources */,
 				589A455C28E094BF00565204 /* OperationSmokeTests.swift in Sources */,
 				589A455D28E094BF00565204 /* OperationObserverTests.swift in Sources */,
+				58AFC99929F97856000829DE /* TransformOperationTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -2627,7 +2642,6 @@
 				5878A27B2909649A0096FC88 /* CustomOverlayRenderer.swift in Sources */,
 				5847D58D29B7740F008C3808 /* RevokedCoordinator.swift in Sources */,
 				588527B2276B3F0700BAA373 /* LoadTunnelConfigurationOperation.swift in Sources */,
-				58F1311527E0B2AB007AC5BC /* Result+Extensions.swift in Sources */,
 				5867770E29096984006F721F /* OutOfTimeInteractor.swift in Sources */,
 				58F185AA298A3E3E00075977 /* TunnelCoordinator.swift in Sources */,
 				58F8AC0E25D3F8CE002BE0ED /* ProblemReportReviewViewController.swift in Sources */,
@@ -2795,7 +2809,6 @@
 			files = (
 				5806767C27048E9B00C858CB /* PacketTunnelProvider.swift in Sources */,
 				587AD7C723421D8600E93A53 /* TunnelSettingsV1.swift in Sources */,
-				06410E09292D990C00AFC18C /* Result+Extensions.swift in Sources */,
 				5893C6FA29C1B481009090D1 /* DNSSettings.swift in Sources */,
 				58CE38C828992C9200A6D6E5 /* TunnelMonitorDelegate.swift in Sources */,
 				068CE5782927BE4800A068BB /* Migration.swift in Sources */,
@@ -2863,6 +2876,7 @@
 				58D22408294C90210029F5F8 /* AnyIPEndpoint.swift in Sources */,
 				58D22409294C90210029F5F8 /* AnyIPAddress.swift in Sources */,
 				58D2240A294C90210029F5F8 /* IPAddress+Codable.swift in Sources */,
+				58E45A5729F12C5100281ECF /* Result+Extensions.swift in Sources */,
 				58D2240B294C90210029F5F8 /* Cancellable.swift in Sources */,
 				58D2240C294C90210029F5F8 /* WrappingError.swift in Sources */,
 				58D2240D294C90210029F5F8 /* CustomErrorDescriptionProtocol.swift in Sources */,
@@ -3043,6 +3057,11 @@
 			target = 5898D28829017BD300EB5EBA /* TunnelProviderMessaging */;
 			targetProxy = 58D22433294C94890029F5F8 /* PBXContainerItemProxy */;
 		};
+		58EED36E29FBEF040000CBAF /* PBXTargetDependency */ = {
+			isa = PBXTargetDependency;
+			target = 58D223D4294C8E5E0029F5F8 /* MullvadTypes */;
+			targetProxy = 58EED36D29FBEF040000CBAF /* PBXContainerItemProxy */;
+		};
 		58FBDAA222A52A6800EB69A3 /* PBXTargetDependency */ = {
 			isa = PBXTargetDependency;
 			target = 58FBDA9722A519BC00EB69A3 /* WireGuardGoBridge */;
diff --git a/ios/MullvadVPN/AddressCacheTracker/AddressCacheTracker.swift b/ios/MullvadVPN/AddressCacheTracker/AddressCacheTracker.swift
index 8c3100f92b..d7c402c802 100644
--- a/ios/MullvadVPN/AddressCacheTracker/AddressCacheTracker.swift
+++ b/ios/MullvadVPN/AddressCacheTracker/AddressCacheTracker.swift
@@ -85,20 +85,16 @@ final class AddressCacheTracker {
     }
 
     func updateEndpoints(completionHandler: ((Result<Bool, Error>) -> Void)? = nil) -> Cancellable {
-        let operation = ResultBlockOperation<Bool> { operation in
+        let operation = ResultBlockOperation<Bool> { finish -> Cancellable in
             guard self.nextScheduleDate() <= Date() else {
-                operation.finish(result: .success(false))
-                return
+                finish(.success(false))
+                return AnyCancellable()
             }
 
-            let task = self.apiProxy.getAddressList(retryStrategy: .default) { result in
+            return self.apiProxy.getAddressList(retryStrategy: .default) { result in
                 self.setEndpoints(from: result)
 
-                operation.finish(result: result.map { _ in true })
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
+                finish(result.map { _ in true })
             }
         }
 
diff --git a/ios/MullvadVPN/AppDelegate.swift b/ios/MullvadVPN/AppDelegate.swift
index 640d7fc86c..233c17d73f 100644
--- a/ios/MullvadVPN/AppDelegate.swift
+++ b/ios/MullvadVPN/AppDelegate.swift
@@ -370,7 +370,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
     private func startInitialization(application: UIApplication) {
         let wipeSettingsOperation = getWipeSettingsOperation()
 
-        let loadTunnelStoreOperation = AsyncBlockOperation(dispatchQueue: .main) { operation in
+        let loadTunnelStoreOperation = AsyncBlockOperation(dispatchQueue: .main) { finish in
             self.tunnelStore.loadPersistentTunnels { error in
                 if let error = error {
                     self.logger.error(
@@ -378,16 +378,14 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
                         message: "Failed to load persistent tunnels."
                     )
                 }
-                operation.finish()
+                finish(nil)
             }
         }
 
-        let migrateSettingsOperation = ResultBlockOperation<SettingsMigrationResult>(
-            dispatchQueue: .main
-        ) { operation in
+        let migrateSettingsOperation = ResultBlockOperation<SettingsMigrationResult>(dispatchQueue: .main) { finish in
             SettingsManager.migrateStore(with: self.proxyFactory) { migrationResult in
                 let finishHandler = {
-                    operation.finish(result: .success(migrationResult))
+                    finish(.success(migrationResult))
                 }
 
                 guard case let .failure(error) = migrationResult,
@@ -404,7 +402,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
         }
         migrateSettingsOperation.addDependencies([wipeSettingsOperation, loadTunnelStoreOperation])
 
-        let initTunnelManagerOperation = AsyncBlockOperation(dispatchQueue: .main) { operation in
+        let initTunnelManagerOperation = AsyncBlockOperation(dispatchQueue: .main) { finish in
             self.tunnelManager.loadConfiguration { error in
                 // TODO: avoid throwing fatal error and show the problem report UI instead.
                 if let error = error {
@@ -416,7 +414,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
                 NotificationManager.shared.updateNotifications()
                 self.storePaymentManager.startPaymentQueueMonitoring()
 
-                operation.finish()
+                finish(nil)
             }
         }
         initTunnelManagerOperation.addDependency(migrateSettingsOperation)
diff --git a/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift b/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
index 75b73b2119..402063052d 100644
--- a/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
+++ b/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
@@ -97,23 +97,16 @@ final class RelayCacheTracker {
     func updateRelays(completionHandler: ((Result<RelaysFetchResult, Error>) -> Void)? = nil)
         -> Cancellable
     {
-        let operation = ResultBlockOperation<RelaysFetchResult>(dispatchQueue: nil) { operation in
+        let operation = ResultBlockOperation<RelaysFetchResult> { finish in
             let cachedRelays = try? self.getCachedRelays()
 
             if self.getNextUpdateDate() > Date() {
-                operation.finish(result: .success(.throttled))
-                return
+                finish(.success(.throttled))
+                return AnyCancellable()
             }
 
-            let task = self.apiProxy.getRelays(
-                etag: cachedRelays?.etag,
-                retryStrategy: .noRetry
-            ) { result in
-                operation.finish(result: self.handleResponse(result: result))
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
+            return self.apiProxy.getRelays(etag: cachedRelays?.etag, retryStrategy: .noRetry) { result in
+                finish(self.handleResponse(result: result))
             }
         }
 
diff --git a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
index 40e1b6b7e3..62ff2f11f9 100644
--- a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
+++ b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
@@ -181,17 +181,12 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
         accountNumber: String,
         completionHandler: @escaping (StorePaymentManagerError?) -> Void
     ) {
-        let accountOperation = ResultBlockOperation<REST.AccountData>(dispatchQueue: .main) { op in
-            let task = self.accountsProxy.getAccountData(
+        let accountOperation = ResultBlockOperation<REST.AccountData>(dispatchQueue: .main) { finish in
+            return self.accountsProxy.getAccountData(
                 accountNumber: accountNumber,
-                retryStrategy: .default
-            ) { result in
-                op.finish(result: result)
-            }
-
-            op.addCancellationBlock {
-                task.cancel()
-            }
+                retryStrategy: .default,
+                completion: finish
+            )
         }
 
         accountOperation.addObserver(BackgroundObserver(
diff --git a/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift b/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
index 4f99c86bdc..e13e4373fe 100644
--- a/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
@@ -9,6 +9,7 @@
 import Foundation
 import MullvadLogging
 import MullvadREST
+import MullvadTypes
 import Operations
 import class WireGuardKitTypes.PrivateKey
 import class WireGuardKitTypes.PublicKey
@@ -183,12 +184,10 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
     }
 
     private func getCreateAccountOperation() -> ResultBlockOperation<StoredAccountData> {
-        let operation = ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue)
-
-        operation.setExecutionBlock { operation in
+        return ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue) { finish -> Cancellable in
             self.logger.debug("Create new account...")
 
-            let task = self.accountsProxy.createAccount(retryStrategy: .default) { result in
+            return self.accountsProxy.createAccount(retryStrategy: .default) { result in
                 let result = result.inspectError { error in
                     guard !error.isOperationCancellationError else { return }
 
@@ -206,55 +205,37 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
                     )
                 }
 
-                operation.finish(result: result)
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
+                finish(result)
             }
         }
-
-        return operation
     }
 
-    private func getExistingAccountOperation(accountNumber: String)
-        -> ResultOperation<StoredAccountData>
-    {
-        let operation = ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue)
-
-        operation.setExecutionBlock { operation in
+    private func getExistingAccountOperation(accountNumber: String) -> ResultOperation<StoredAccountData> {
+        return ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue) { finish -> Cancellable in
             self.logger.debug("Request account data...")
 
-            let task = self.accountsProxy.getAccountData(
-                accountNumber: accountNumber,
-                retryStrategy: .default
-            ) { result in
-                let result = result.inspectError { error in
-                    guard !error.isOperationCancellationError else { return }
-
-                    self.logger.error(
-                        error: error,
-                        message: "Failed to receive account data."
-                    )
-                }.map { accountData -> StoredAccountData in
-                    self.logger.debug("Received account data.")
+            return self.accountsProxy
+                .getAccountData(accountNumber: accountNumber, retryStrategy: .default) { result in
+                    let result = result.inspectError { error in
+                        guard !error.isOperationCancellationError else { return }
 
-                    return StoredAccountData(
-                        identifier: accountData.id,
-                        number: accountNumber,
-                        expiry: accountData.expiry
-                    )
-                }
+                        self.logger.error(
+                            error: error,
+                            message: "Failed to receive account data."
+                        )
+                    }.map { accountData -> StoredAccountData in
+                        self.logger.debug("Received account data.")
 
-                operation.finish(result: result)
-            }
+                        return StoredAccountData(
+                            identifier: accountData.id,
+                            number: accountNumber,
+                            expiry: accountData.expiry
+                        )
+                    }
 
-            operation.addCancellationBlock {
-                task.cancel()
-            }
+                    finish(result)
+                }
         }
-
-        return operation
     }
 
     private func getDeleteDeviceOperation() -> AsyncBlockOperation? {
@@ -262,12 +243,10 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
             return nil
         }
 
-        let operation = AsyncBlockOperation(dispatchQueue: dispatchQueue)
-
-        operation.setExecutionBlock { operation in
+        let operation = AsyncBlockOperation(dispatchQueue: dispatchQueue) { finish -> Cancellable in
             self.logger.debug("Delete current device...")
 
-            let task = self.devicesProxy.deleteDevice(
+            return self.devicesProxy.deleteDevice(
                 accountNumber: accountData.number,
                 identifier: deviceData.identifier,
                 retryStrategy: .default
@@ -286,11 +265,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
                     break
                 }
 
-                operation.finish(error: result.error)
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
+                finish(result.error)
             }
         }
 
@@ -298,7 +273,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
     }
 
     private func getUnsetDeviceStateOperation() -> AsyncBlockOperation {
-        return AsyncBlockOperation(dispatchQueue: dispatchQueue) { operation in
+        return AsyncBlockOperation(dispatchQueue: dispatchQueue) { finish in
             // Tell the caller to unsubscribe from VPN status notifications.
             self.interactor.prepareForVPNConfigurationDeletion()
 
@@ -311,7 +286,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
 
             // Finish immediately if tunnel provider is not set.
             guard let tunnel = self.interactor.tunnel else {
-                operation.finish()
+                finish(nil)
                 return
             }
 
@@ -328,21 +303,17 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
 
                     self.interactor.setTunnel(nil, shouldRefreshTunnelState: false)
 
-                    operation.finish()
+                    finish(nil)
                 }
             }
         }
     }
 
-    private func getCreateDeviceOperation()
-        -> TransformOperation<StoredAccountData, (PrivateKey, REST.Device)>
-    {
-        let createDeviceOperation = TransformOperation<
-            StoredAccountData,
-            (PrivateKey, REST.Device)
-        >(dispatchQueue: dispatchQueue)
-
-        createDeviceOperation.setExecutionBlock { storedAccountData, operation in
+    private func getCreateDeviceOperation() -> TransformOperation<StoredAccountData, (PrivateKey, REST.Device)> {
+        return TransformOperation<StoredAccountData, (
+            PrivateKey,
+            REST.Device
+        )>(dispatchQueue: dispatchQueue) { storedAccountData, finish -> Cancellable in
             self.logger.debug("Store last used account.")
 
             do {
@@ -363,7 +334,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
                 hijackDNS: false
             )
 
-            let task = self.devicesProxy.createDevice(
+            return self.devicesProxy.createDevice(
                 accountNumber: storedAccountData.number,
                 request: request,
                 retryStrategy: .default
@@ -376,26 +347,13 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
                         self.logger.error(error: error, message: "Failed to create device.")
                     }
 
-                operation.finish(result: result)
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
+                finish(result)
             }
         }
-
-        return createDeviceOperation
     }
 
-    private func getSaveSettingsOperation()
-        -> TransformOperation<SetAccountResult, StoredAccountData>
-    {
-        let saveSettingsOperation = TransformOperation<
-            SetAccountResult,
-            StoredAccountData
-        >(dispatchQueue: dispatchQueue)
-
-        saveSettingsOperation.setExecutionBlock { input in
+    private func getSaveSettingsOperation() -> TransformOperation<SetAccountResult, StoredAccountData> {
+        return TransformOperation<SetAccountResult, StoredAccountData>(dispatchQueue: dispatchQueue) { input in
             self.logger.debug("Saving settings...")
 
             let device = input.device
@@ -421,7 +379,5 @@ class SetAccountOperation: ResultOperation<StoredAccountData?> {
 
             return input.accountData
         }
-
-        return saveSettingsOperation
     }
 }
diff --git a/ios/MullvadVPN/TunnelManager/TunnelManager.swift b/ios/MullvadVPN/TunnelManager/TunnelManager.swift
index 9c9190200b..b2644dcec0 100644
--- a/ios/MullvadVPN/TunnelManager/TunnelManager.swift
+++ b/ios/MullvadVPN/TunnelManager/TunnelManager.swift
@@ -268,24 +268,21 @@ final class TunnelManager: StorePaymentObserver {
     }
 
     func reconnectTunnel(selectNewRelay: Bool, completionHandler: ((Error?) -> Void)? = nil) {
-        let operation = AsyncBlockOperation(dispatchQueue: internalQueue) { operation in
-            guard let tunnel = self.tunnel else {
-                operation.finish(error: UnsetTunnelError())
-                return
-            }
-
+        let operation = AsyncBlockOperation(dispatchQueue: internalQueue) { finish -> Cancellable in
             do {
-                let selectorResult = selectNewRelay ? try self.selectRelay() : nil
-
-                let task = tunnel.reconnectTunnel(relaySelectorResult: selectorResult) { result in
-                    operation.finish(error: result.error)
+                guard let tunnel = self.tunnel else {
+                    throw UnsetTunnelError()
                 }
 
-                operation.addCancellationBlock {
-                    task.cancel()
+                let selectorResult = selectNewRelay ? try self.selectRelay() : nil
+
+                return tunnel.reconnectTunnel(relaySelectorResult: selectorResult) { result in
+                    finish(result.error)
                 }
             } catch {
-                operation.finish(error: error)
+                finish(error)
+
+                return AnyCancellable()
             }
         }
 
diff --git a/ios/MullvadVPN/View controllers/Tunnel/MapViewController.swift b/ios/MullvadVPN/View controllers/Tunnel/MapViewController.swift
index 243672597a..bff8888133 100644
--- a/ios/MullvadVPN/View controllers/Tunnel/MapViewController.swift
+++ b/ios/MullvadVPN/View controllers/Tunnel/MapViewController.swift
@@ -234,9 +234,9 @@ final class MapViewController: UIViewController, MKMapViewDelegate {
         cancelOtherAnimations: Bool,
         block: @escaping (_ finish: @escaping () -> Void) -> Void
     ) {
-        let operation = AsyncBlockOperation(dispatchQueue: .main) { operation in
+        let operation = AsyncBlockOperation(dispatchQueue: .main) { finish in
             block {
-                operation.finish()
+                finish(nil)
             }
         }
 
diff --git a/ios/Operations/AsyncBlockOperation.swift b/ios/Operations/AsyncBlockOperation.swift
index 43be9b8275..062fc528f5 100644
--- a/ios/Operations/AsyncBlockOperation.swift
+++ b/ios/Operations/AsyncBlockOperation.swift
@@ -7,78 +7,53 @@
 //
 
 import Foundation
+import protocol MullvadTypes.Cancellable
 
 /// Asynchronous block operation
 public class AsyncBlockOperation: AsyncOperation {
-    private var executionBlock: ((AsyncBlockOperation) -> Void)?
-    private var cancellationBlocks: [() -> Void] = []
+    private var executor: ((@escaping (Error?) -> Void) -> Cancellable?)?
+    private var cancellableTask: Cancellable?
 
-    override public init(dispatchQueue: DispatchQueue? = nil) {
-        super.init(dispatchQueue: dispatchQueue)
-    }
-
-    public init(
-        dispatchQueue: DispatchQueue? = nil,
-        block: @escaping (AsyncBlockOperation) -> Void
-    ) {
-        executionBlock = block
+    public init(dispatchQueue: DispatchQueue? = nil, block: @escaping (@escaping (Error?) -> Void) -> Void) {
         super.init(dispatchQueue: dispatchQueue)
+        executor = { finish in
+            block(finish)
+            return nil
+        }
     }
 
     public init(dispatchQueue: DispatchQueue? = nil, block: @escaping () -> Void) {
-        executionBlock = { operation in
+        super.init(dispatchQueue: dispatchQueue)
+        executor = { finish in
             block()
-            operation.finish()
+            finish(nil)
+            return nil
         }
+    }
+
+    public init(
+        dispatchQueue: DispatchQueue? = nil,
+        cancellableTask: @escaping (@escaping (Error?) -> Void) -> Cancellable
+    ) {
         super.init(dispatchQueue: dispatchQueue)
+        executor = { cancellableTask($0) }
     }
 
     override public func main() {
-        let block = executionBlock
-        executionBlock = nil
+        let executor = executor
+        self.executor = nil
 
-        if let block = block {
-            block(self)
-        } else {
-            finish()
-        }
+        assert(executor != nil)
+
+        cancellableTask = executor?(self.finish)
     }
 
     override public func operationDidCancel() {
-        let blocks = cancellationBlocks
-        cancellationBlocks.removeAll()
-
-        for block in blocks {
-            block()
-        }
+        cancellableTask?.cancel()
     }
 
     override public func operationDidFinish() {
-        cancellationBlocks.removeAll()
-        executionBlock = nil
-    }
-
-    public func setExecutionBlock(_ block: @escaping (AsyncBlockOperation) -> Void) {
-        dispatchQueue.async {
-            assert(!self.isExecuting && !self.isFinished)
-            self.executionBlock = block
-        }
-    }
-
-    public func setExecutionBlock(_ block: @escaping () -> Void) {
-        setExecutionBlock { operation in
-            block()
-            operation.finish()
-        }
-    }
-
-    public func addCancellationBlock(_ block: @escaping () -> Void) {
-        dispatchQueue.async {
-            if self.isCancelled, self.isExecuting {
-                block()
-            } else {
-                self.cancellationBlocks.append(block)
-            }
-        }
+        executor = nil
+        cancellableTask = nil
     }
 }
diff --git a/ios/Operations/AsyncOperation.swift b/ios/Operations/AsyncOperation.swift
index 2ca049030c..ca11e86d7e 100644
--- a/ios/Operations/AsyncOperation.swift
+++ b/ios/Operations/AsyncOperation.swift
@@ -436,6 +436,11 @@ extension OperationBlockObserverSupport where Self: AsyncOperation {
         addBlockObserver(OperationBlockObserver(didFinish: fn))
     }
 
+    /// Add observer responding to start event.
+    public func onStart(_ fn: @escaping (Self) -> Void) {
+        addBlockObserver(OperationBlockObserver(didStart: fn))
+    }
+
     /// Add block-based observer.
     public func addBlockObserver(_ observer: OperationBlockObserver<Self>) {
         addObserver(observer)
diff --git a/ios/Operations/ResultBlockOperation.swift b/ios/Operations/ResultBlockOperation.swift
index 5d848b438d..867dee45cf 100644
--- a/ios/Operations/ResultBlockOperation.swift
+++ b/ios/Operations/ResultBlockOperation.swift
@@ -7,102 +7,53 @@
 //
 
 import Foundation
+import protocol MullvadTypes.Cancellable
 
 public final class ResultBlockOperation<Success>: ResultOperation<Success> {
-    public typealias ExecutionBlock = (ResultBlockOperation<Success>) -> Void
-    public typealias ThrowingExecutionBlock = () throws -> Success
+    private var executor: ((@escaping (Result<Success, Error>) -> Void) -> Cancellable?)?
+    private var cancellableTask: Cancellable?
 
-    private var executionBlock: ExecutionBlock?
-    private var cancellationBlocks: [() -> Void] = []
-
-    public convenience init(
+    public init(
         dispatchQueue: DispatchQueue? = nil,
-        executionBlock: ExecutionBlock? = nil
+        executionBlock: @escaping (_ finish: @escaping (Result<Success, Error>) -> Void) -> Void
     ) {
-        self.init(
-            dispatchQueue: dispatchQueue,
-            executionBlock: executionBlock,
-            completionQueue: nil,
-            completionHandler: nil
-        )
+        super.init(dispatchQueue: dispatchQueue)
+        executor = { finish in
+            executionBlock(finish)
+            return nil
+        }
     }
 
-    public convenience init(
-        dispatchQueue: DispatchQueue? = nil,
-        executionBlock: @escaping ThrowingExecutionBlock
-    ) {
-        self.init(
-            dispatchQueue: dispatchQueue,
-            executionBlock: Self.wrapThrowingBlock(executionBlock),
-            completionQueue: nil,
-            completionHandler: nil
-        )
+    public init(dispatchQueue: DispatchQueue? = nil, executionBlock: @escaping () throws -> Success) {
+        super.init(dispatchQueue: dispatchQueue)
+        executor = { finish in
+            finish(Result { try executionBlock() })
+            return nil
+        }
     }
 
     public init(
-        dispatchQueue: DispatchQueue?,
-        executionBlock: ExecutionBlock?,
-        completionQueue: DispatchQueue?,
-        completionHandler: CompletionHandler?
+        dispatchQueue: DispatchQueue? = nil,
+        cancellableTask: @escaping (_ finish: @escaping (Result<Success, Error>) -> Void) -> Cancellable
     ) {
-        self.executionBlock = executionBlock
-
-        super.init(
-            dispatchQueue: dispatchQueue,
-            completionQueue: completionQueue,
-            completionHandler: completionHandler
-        )
+        super.init(dispatchQueue: dispatchQueue)
+        executor = { cancellableTask($0) }
     }
 
     override public func main() {
-        let block = executionBlock
-        executionBlock = nil
+        let executor = executor
+        self.executor = nil
 
-        block?(self)
+        assert(executor != nil)
+        cancellableTask = executor?(self.finish)
     }
 
     override public func operationDidCancel() {
-        let blocks = cancellationBlocks
-        cancellationBlocks.removeAll()
-
-        for block in blocks {
-            block()
-        }
+        cancellableTask?.cancel()
     }
 
     override public func operationDidFinish() {
-        cancellationBlocks.removeAll()
-        executionBlock = nil
-    }
-
-    public func setExecutionBlock(_ block: @escaping ExecutionBlock) {
-        dispatchQueue.async {
-            assert(!self.isExecuting && !self.isFinished)
-            self.executionBlock = block
-        }
-    }
-
-    public func setExecutionBlock(_ block: @escaping ThrowingExecutionBlock) {
-        setExecutionBlock(Self.wrapThrowingBlock(block))
-    }
-
-    public func addCancellationBlock(_ block: @escaping () -> Void) {
-        dispatchQueue.async {
-            if self.isCancelled, self.isExecuting {
-                block()
-            } else {
-                self.cancellationBlocks.append(block)
-            }
-        }
-    }
-
-    private class func wrapThrowingBlock(_ executionBlock: @escaping ThrowingExecutionBlock)
-        -> ExecutionBlock
-    {
-        return { operation in
-            let result = Result { try executionBlock() }
-
-            operation.finish(result: result)
-        }
+        executor = nil
+        cancellableTask = nil
     }
 }
diff --git a/ios/Operations/TransformOperation.swift b/ios/Operations/TransformOperation.swift
index 609e07896c..b5cc36adad 100644
--- a/ios/Operations/TransformOperation.swift
+++ b/ios/Operations/TransformOperation.swift
@@ -7,10 +7,9 @@
 //
 
 import Foundation
+import protocol MullvadTypes.Cancellable
 
 public final class TransformOperation<Input, Output>: ResultOperation<Output>, InputOperation {
-    public typealias ExecutionBlock = (Input, TransformOperation<Input, Output>) -> Void
-    public typealias ThrowingExecutionBlock = (Input) throws -> Output
     public typealias InputBlock = () -> Input?
 
     private let nslock = NSLock()
@@ -35,79 +34,70 @@ public final class TransformOperation<Input, Output>: ResultOperation<Output>, I
 
     private var inputBlock: InputBlock?
 
-    private var executionBlock: ExecutionBlock?
-    private var cancellationBlocks: [() -> Void] = []
+    private var executor: ((Input, @escaping (Result<Output, Error>) -> Void) -> Cancellable?)?
+    private var cancellableTask: Cancellable?
 
     public init(
         dispatchQueue: DispatchQueue? = nil,
         input: Input? = nil,
-        block: ExecutionBlock? = nil
+        block: @escaping (_ input: Input, _ finish: @escaping (Result<Output, Error>) -> Void) -> Void
     ) {
-        __input = input
-        executionBlock = block
-
         super.init(dispatchQueue: dispatchQueue)
+        __input = input
+        executor = { input, finish in
+            block(input, finish)
+            return nil
+        }
     }
 
     public init(
         dispatchQueue: DispatchQueue? = nil,
         input: Input? = nil,
-        throwingBlock: @escaping ThrowingExecutionBlock
+        throwingBlock: @escaping (_ input: Input) throws -> Output
     ) {
+        super.init(dispatchQueue: dispatchQueue)
         __input = input
-        executionBlock = Self.wrapThrowingBlock(throwingBlock)
+        executor = { input, finish in
+            finish(Result { try throwingBlock(input) })
+            return nil
+        }
+    }
 
+    public init(
+        dispatchQueue: DispatchQueue? = nil,
+        input: Input? = nil,
+        cancellableTask: @escaping (_ input: Input, _ finish: @escaping (Result<Output, Error>) -> Void) -> Cancellable
+    ) {
         super.init(dispatchQueue: dispatchQueue)
+        __input = input
+        executor = cancellableTask
     }
 
     override public func main() {
-        let inputValue = inputBlock?()
-
-        _input = inputValue
+        if let inputBlock = inputBlock {
+            _input = inputBlock()
+        }
 
-        guard let inputValue = inputValue, let executionBlock = executionBlock else {
+        guard let inputValue = _input else {
             finish(result: .failure(OperationError.unsatisfiedRequirement))
             return
         }
 
-        executionBlock(inputValue, self)
-    }
+        let executor = executor
+        self.executor = nil
 
-    override public func operationDidCancel() {
-        let blocks = cancellationBlocks
-        cancellationBlocks.removeAll()
+        assert(executor != nil)
 
-        for block in blocks {
-            block()
-        }
+        cancellableTask = executor?(inputValue, self.finish)
     }
 
-    override public func operationDidFinish() {
-        cancellationBlocks.removeAll()
-        executionBlock = nil
-    }
-
-    // MARK: - Block handlers
-
-    public func setExecutionBlock(_ block: @escaping ExecutionBlock) {
-        dispatchQueue.async {
-            assert(!self.isExecuting && !self.isFinished)
-            self.executionBlock = block
-        }
-    }
-
-    public func setExecutionBlock(_ block: @escaping ThrowingExecutionBlock) {
-        setExecutionBlock(Self.wrapThrowingBlock(block))
+    override public func operationDidCancel() {
+        cancellableTask?.cancel()
     }
 
-    public func addCancellationBlock(_ block: @escaping () -> Void) {
-        dispatchQueue.async {
-            if self.isCancelled, self.isExecuting {
-                block()
-            } else {
-                self.cancellationBlocks.append(block)
-            }
-        }
+    override public func operationDidFinish() {
+        executor = nil
+        cancellableTask = nil
     }
 
     // MARK: - Input injection
@@ -117,14 +107,4 @@ public final class TransformOperation<Input, Output>: ResultOperation<Output>, I
             self.inputBlock = block
         }
     }
-
-    private class func wrapThrowingBlock(_ executionBlock: @escaping ThrowingExecutionBlock)
-        -> ExecutionBlock
-    {
-        return { input, operation in
-            let result = Result { try executionBlock(input) }
-
-            operation.finish(result: result)
-        }
-    }
 }
diff --git a/ios/OperationsTests/AsyncBlockOperationTests.swift b/ios/OperationsTests/AsyncBlockOperationTests.swift
new file mode 100644
index 0000000000..07a65d0ccd
--- /dev/null
+++ b/ios/OperationsTests/AsyncBlockOperationTests.swift
@@ -0,0 +1,99 @@
+//
+//  AsyncBlockOperationTests.swift
+//  OperationsTests
+//
+//  Created by pronebird on 26/04/2023.
+//  Copyright © 2023 Mullvad VPN AB. All rights reserved.
+//
+
+import MullvadTypes
+import Operations
+import XCTest
+
+final class AsyncBlockOperationTests: XCTestCase {
+    let operationQueue = AsyncOperationQueue()
+
+    func testBlockOperation() {
+        let executionExpectation = expectation(description: "Should execute")
+        let finishExpectation = expectation(description: "Should finish")
+
+        let operation = AsyncBlockOperation(block: { finish in
+            executionExpectation.fulfill()
+            finish(nil)
+        })
+
+        operation.completionBlock = {
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testSynchronousBlockOperation() {
+        let executionExpectation = expectation(description: "Should execute")
+        let finishExpectation = expectation(description: "Should finish")
+
+        let operation = AsyncBlockOperation {
+            executionExpectation.fulfill()
+        }
+
+        operation.completionBlock = {
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testCancellableTaskBlockOperation() {
+        let executionExpectation = expectation(description: "Should execute")
+        let cancelExpectation = expectation(description: "Should cancel")
+        let finishExpectation = expectation(description: "Should finish")
+
+        let operation = AsyncBlockOperation { finish -> Cancellable in
+            executionExpectation.fulfill()
+
+            return AnyCancellable {
+                cancelExpectation.fulfill()
+                finish(nil)
+            }
+        }
+
+        operation.completionBlock = {
+            finishExpectation.fulfill()
+        }
+
+        operation.onStart { op in
+            op.cancel()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testCancellationShouldNotFireBeforeOperationIsEnqueued() throws {
+        let expect = expectation(description: "Cancellation should not fire.")
+        expect.isInverted = true
+
+        let operation = AsyncBlockOperation {}
+        operation.onCancel { _ in expect.fulfill() }
+        operation.cancel()
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testCancellationShouldFireAfterCancelledOperationIsEnqueued() throws {
+        let expect = expectation(description: "Cancellation should fire.")
+
+        let operation = AsyncBlockOperation {}
+        operation.onCancel { _ in expect.fulfill() }
+        operation.cancel()
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+}
diff --git a/ios/OperationsTests/AsyncResultBlockOperationTests.swift b/ios/OperationsTests/AsyncResultBlockOperationTests.swift
new file mode 100644
index 0000000000..5bae7f7d9c
--- /dev/null
+++ b/ios/OperationsTests/AsyncResultBlockOperationTests.swift
@@ -0,0 +1,75 @@
+//
+//  AsyncResultBlockOperationTests.swift
+//  OperationsTests
+//
+//  Created by pronebird on 26/04/2023.
+//  Copyright © 2023 Mullvad VPN AB. All rights reserved.
+//
+
+import MullvadTypes
+import Operations
+import XCTest
+
+final class AsyncResultBlockOperationTests: XCTestCase {
+    let operationQueue = AsyncOperationQueue()
+
+    func testBlockOperation() {
+        let expectation = expectation(description: "Should finish")
+
+        let operation = ResultBlockOperation<Bool> { finish in
+            finish(.success(true))
+        }
+
+        operation.onFinish { op, error in
+            XCTAssertEqual(op.result?.value, true)
+            expectation.fulfill()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testThrowingBlockOperation() {
+        let expectation = expectation(description: "Should finish")
+
+        let operation = ResultBlockOperation {
+            throw URLError(.badURL)
+        }
+
+        operation.onFinish { op, error in
+            XCTAssertEqual(op.result?.error as? URLError, URLError(.badURL))
+            XCTAssertEqual(error as? URLError, URLError(.badURL))
+
+            expectation.fulfill()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testCancellableTaskOperation() {
+        let expectation = expectation(description: "Should finish")
+
+        let operation = ResultBlockOperation<Bool> { finish -> Cancellable in
+            return AnyCancellable {
+                finish(.failure(URLError(.cancelled)))
+            }
+        }
+
+        operation.onStart { op in
+            op.cancel()
+        }
+
+        operation.onFinish { op, error in
+            XCTAssertEqual(op.result?.error as? URLError, URLError(.cancelled))
+            XCTAssertEqual(error as? URLError, URLError(.cancelled))
+            expectation.fulfill()
+        }
+
+        operationQueue.addOperation(operation)
+
+        waitForExpectations(timeout: 1)
+    }
+}
diff --git a/ios/OperationsTests/OperationCancellationTests.swift b/ios/OperationsTests/OperationCancellationTests.swift
deleted file mode 100644
index 7313bc83b2..0000000000
--- a/ios/OperationsTests/OperationCancellationTests.swift
+++ /dev/null
@@ -1,35 +0,0 @@
-//
-//  OperationCancellationTests.swift
-//  OperationsTests
-//
-//  Created by pronebird on 12/04/2023.
-//  Copyright © 2023 Mullvad VPN AB. All rights reserved.
-//
-
-import Operations
-import XCTest
-
-final class OperationCancellationTests: XCTestCase {
-    func testCancellationShouldNotFireBeforeOperationIsEnqueued() throws {
-        let expect = expectation(description: "Cancellation should not fire.")
-        expect.isInverted = true
-
-        let operation = AsyncBlockOperation {}
-        operation.onCancel { _ in expect.fulfill() }
-        operation.cancel()
-
-        waitForExpectations(timeout: 1)
-    }
-
-    func testCancellationShouldFireAfterCancelledOperationIsEnqueued() throws {
-        let expect = expectation(description: "Cancellation should fire.")
-
-        let operationQueue = AsyncOperationQueue()
-        let operation = AsyncBlockOperation {}
-        operation.onCancel { _ in expect.fulfill() }
-        operation.cancel()
-        operationQueue.addOperation(operation)
-
-        waitForExpectations(timeout: 1)
-    }
-}
diff --git a/ios/OperationsTests/OperationConditionTests.swift b/ios/OperationsTests/OperationConditionTests.swift
index b35e687319..27898ea424 100644
--- a/ios/OperationsTests/OperationConditionTests.swift
+++ b/ios/OperationsTests/OperationConditionTests.swift
@@ -123,10 +123,10 @@ class OperationConditionTests: XCTestCase {
         let exclusiveCategory = "exclusiveOperations"
         let operationQueue = AsyncOperationQueue()
 
-        let firstOperation = AsyncBlockOperation { op in
+        let firstOperation = AsyncBlockOperation { finish in
             DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(1)) {
                 expectFirstOperationExecution.fulfill()
-                op.finish()
+                finish(nil)
             }
         }
         firstOperation.addCondition(MutuallyExclusive(category: exclusiveCategory))
diff --git a/ios/OperationsTests/OperationObserverTests.swift b/ios/OperationsTests/OperationObserverTests.swift
index c246cdc526..de334be21a 100644
--- a/ios/OperationsTests/OperationObserverTests.swift
+++ b/ios/OperationsTests/OperationObserverTests.swift
@@ -17,7 +17,7 @@ class OperationObserverTests: XCTestCase {
         expectDidCancel.isInverted = true
         let expectDidFinish = expectation(description: "didAttach handler")
 
-        let operation = AsyncBlockOperation()
+        let operation = AsyncBlockOperation {}
         operation.addBlockObserver(OperationBlockObserver(
             didAttach: { op in
                 expectDidAttach.fulfill()
@@ -44,7 +44,7 @@ class OperationObserverTests: XCTestCase {
         let expectDidCancel = expectation(description: "didCancel handler")
         let expectDidFinish = expectation(description: "didAttach handler")
 
-        let operation = AsyncBlockOperation()
+        let operation = AsyncBlockOperation {}
         operation.addBlockObserver(OperationBlockObserver(
             didAttach: { op in
                 expectDidAttach.fulfill()
diff --git a/ios/OperationsTests/TransformOperationTests.swift b/ios/OperationsTests/TransformOperationTests.swift
new file mode 100644
index 0000000000..c16bcd3be1
--- /dev/null
+++ b/ios/OperationsTests/TransformOperationTests.swift
@@ -0,0 +1,93 @@
+//
+//  TransformOperationTests.swift
+//  OperationsTests
+//
+//  Created by pronebird on 26/04/2023.
+//  Copyright © 2023 Mullvad VPN AB. All rights reserved.
+//
+
+import MullvadTypes
+import Operations
+import XCTest
+
+final class TransformOperationTests: XCTestCase {
+    let operationQueue = AsyncOperationQueue()
+
+    func testBlockTransformOperation() {
+        let finishExpectation = expectation(description: "Should finish")
+
+        let transform = TransformOperation(input: Int.zero) { input, finish in
+            finish(.success(input + 1))
+        }
+
+        transform.onFinish { op, error in
+            XCTAssertEqual(op.result?.value, 1)
+
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(transform)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testThrowingBlockTransformOperation() {
+        let finishExpectation = expectation(description: "Should finish")
+
+        let transform = TransformOperation(input: Int.zero) { value in
+            throw URLError(.badURL)
+        }
+
+        transform.onFinish { op, error in
+            XCTAssertEqual(error as? URLError, URLError(.badURL))
+
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(transform)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testCancellableTaskBlockTransformOperation() {
+        let finishExpectation = expectation(description: "Should finish")
+
+        let transform = TransformOperation<Int, Int>(input: Int.zero) { _, finish -> Cancellable in
+            return AnyCancellable {
+                finish(.failure(URLError(.cancelled)))
+            }
+        }
+
+        transform.onStart { op in
+            op.cancel()
+        }
+
+        transform.onFinish { op, error in
+            XCTAssertEqual(error as? URLError, URLError(.cancelled))
+
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(transform)
+
+        waitForExpectations(timeout: 1)
+    }
+
+    func testShouldFailWithUnsatisfiedRequirement() {
+        let finishExpectation = expectation(description: "Should finish")
+
+        let transform = TransformOperation<Int, Int> { input, finish in
+            finish(.success(input))
+        }
+
+        transform.onFinish { _, error in
+            XCTAssertEqual(error as? OperationError, .unsatisfiedRequirement)
+
+            finishExpectation.fulfill()
+        }
+
+        operationQueue.addOperation(transform)
+
+        waitForExpectations(timeout: 1)
+    }
+}
diff --git a/ios/PacketTunnel/PacketTunnelProvider.swift b/ios/PacketTunnel/PacketTunnelProvider.swift
index 380293695b..c70d5e0d35 100644
--- a/ios/PacketTunnel/PacketTunnelProvider.swift
+++ b/ios/PacketTunnel/PacketTunnelProvider.swift
@@ -585,16 +585,16 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
         // Ignore all requests to reconnect once tunnel is preparing to stop.
         guard !isStopping else { return }
 
-        let blockOperation = AsyncBlockOperation(dispatchQueue: dispatchQueue) { operation in
+        let blockOperation = AsyncBlockOperation(dispatchQueue: dispatchQueue, block: { finish in
             if shouldStopTunnelMonitor {
                 self.tunnelMonitor.stop()
             }
 
             self.reconnectTunnelInner(to: nextRelay) { error in
                 completionHandler?(error)
-                operation.finish()
+                finish(nil)
             }
-        }
+        })
 
         if let reconnectTunnelTask = reconnectTunnelTask {
             blockOperation.addDependency(reconnectTunnelTask)
@@ -779,49 +779,28 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
         operationQueue.addOperation(groupOperation)
     }
 
-    private func createGetAccountDataOperation(accountNumber: String)
-        -> ResultOperation<REST.AccountData>
-    {
-        let operation = ResultBlockOperation<REST.AccountData>(
-            dispatchQueue: dispatchQueue
-        )
-
-        operation.setExecutionBlock { operation in
-            let task = self.accountsProxy.getAccountData(
+    private func createGetAccountDataOperation(accountNumber: String) -> ResultOperation<REST.AccountData> {
+        return ResultBlockOperation<REST.AccountData>(dispatchQueue: dispatchQueue) { finish -> Cancellable in
+            return self.accountsProxy.getAccountData(
                 accountNumber: accountNumber,
-                retryStrategy: .noRetry
-            ) { result in
-                operation.finish(result: result)
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
-            }
+                retryStrategy: .noRetry,
+                completion: finish
+            )
         }
-
-        return operation
     }
 
-    private func createGetDeviceDataOperation(accountNumber: String, identifier: String)
-        -> ResultOperation<REST.Device>
-    {
-        let operation = ResultBlockOperation<REST.Device>(dispatchQueue: dispatchQueue)
-
-        operation.setExecutionBlock { operation in
-            let task = self.devicesProxy.getDevice(
+    private func createGetDeviceDataOperation(
+        accountNumber: String,
+        identifier: String
+    ) -> ResultOperation<REST.Device> {
+        return ResultBlockOperation<REST.Device>(dispatchQueue: dispatchQueue) { finish -> Cancellable in
+            return self.devicesProxy.getDevice(
                 accountNumber: accountNumber,
                 identifier: identifier,
-                retryStrategy: .noRetry
-            ) { result in
-                operation.finish(result: result)
-            }
-
-            operation.addCancellationBlock {
-                task.cancel()
-            }
+                retryStrategy: .noRetry,
+                completion: finish
+            )
         }
-
-        return operation
     }
 }