Add concurrency task lifecycle binding to interactor

Sources/IMVVM/AnyCancellable+Interactor.swift

@@ -21,6 +21,7 @@
 // SOFTWARE.
 
 import Combine
+import Foundation
 
 extension AnyCancellable {
   /// When the interactor deinits, the subscription is cancelled.

Sources/IMVVM/Task+Interactor.swift

@@ -0,0 +1,94 @@
+// MIT License
+//
+// Copyright (c) 2022 Yi Wang
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+import Combine
+import Foundation
+
+extension Task: Cancellable {}
+
+extension Task {
+  /// When the interactor deinits, the task is cancelled.
+  ///
+  /// This function provides the utility to manage Task lifecycle inside a `Interactor` implementation. For
+  /// example:
+  ///
+  ///     class MyInteractor: Interactor {
+  ///       func buttonDidTap() {
+  ///         Task {
+  ///           ...
+  ///         }
+  ///         .cancelOnDeinit(of: self)
+  ///       }
+  ///     }
+  ///
+  /// - Note: Because this function causes the given interactor to stongly retain the task, this means the task
+  /// itself should not strongly retain the interactor. Otherwise a retain cycle would occur causing memory leaks.
+  ///
+  /// This function is thread-safe. Invocations of this function to the same interactor instance can be performed on
+  /// the different threads.
+  ///
+  /// This function can only be invoked after the given interactor has loaded. This is done via the interactor's
+  /// `viewDidAppear` function. Generally speaking, this interactor should be bound to the lifecycle of a `View`.
+  /// See `ViewLifecycleObserver` for more details.
+  ///
+  /// - Parameters:
+  ///   - interactor: The interactor to bind the task's lifecycle to.
+  public func cancelOnDeinit<InteractorType: Interactor>(of interactor: InteractorType) {
+    if !interactor.isLoaded {
+      fatalError("\(interactor) has not been loaded")
+    }
+    interactor.deinitCancelBag.store(AnyCancellable(self))
+  }
+
+  /// When the interactor's view disappears, the task is cancelled.
+  ///
+  /// This function provides the utility to manage Task lifecycle inside a `Interactor` implementation. For
+  /// example:
+  ///
+  ///     class MyInteractor: Interactor {
+  ///       func buttonDidTap() {
+  ///         Task {
+  ///           ...
+  ///         }
+  ///         .cancelOnViewDidDisappear(of: self)
+  ///       }
+  ///     }
+  ///
+  /// - Note: Because this function causes the given interactor to stongly retain the task, this means the task
+  /// itself should not strongly retain the interactor. Otherwise a retain cycle would occur causing memory leaks.
+  ///
+  /// This function is thread-safe. Invocations of this function to the same interactor instance can be performed on
+  /// the different threads.
+  ///
+  /// This function can only be invoked after the given interactor has received notification that its view has
+  /// appeared. This is done via the interactor's `viewDidAppear` function. Generally speaking, this interactor
+  /// should be bound to the lifecycle of a `View`. See `ViewLifecycleObserver` for more details.
+  ///
+  /// - Parameters:
+  ///   - interactor: The interactor to bind the task's lifecycle to.
+  public func cancelOnViewDidDisappear<InteractorType: Interactor>(of interactor: InteractorType) {
+    if !interactor.hasViewAppeared {
+      fatalError("\(interactor)'s view has not appeared")
+    }
+    interactor.viewAppearanceCancelBag.store(AnyCancellable(self))
+  }
+}