task.swift

import Cocoa
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

class A { // Taskでselfを使わないパターン

    var task: Task<Void, Error>?

    init() {
        print("init")
    }

    func start() {
        print("start")
        task = Task {
            try await Task.sleep(nanoseconds: NSEC_PER_SEC)
            print("done without self")
        }
    }

    deinit {
        print("deinit")
        task?.cancel()
    }
}

autoreleasepool {
    let a = A()
    a.start()
    print(a)
}

// init
// start
// __lldb_expr_91.A
// deinit

Thread.sleep(forTimeInterval: 1)
print("====================")

class B { // Taskで最後までselfを使うパターン

    var task: Task<Void, Error>?

    init() {
        print("init")
    }

    func start() {
        print("start")
        task = Task {
            try await Task.sleep(nanoseconds: NSEC_PER_SEC / 2)
            print("done with self: \(self)")
        }
    }

    deinit {
        print("deinit")
        task?.cancel()
    }
}

autoreleasepool {
    let b = B()
    b.start()
    print(b)
}

// init
// start
// __lldb_expr_91.B
// done with self: __lldb_expr_91.B
// deinit

Thread.sleep(forTimeInterval: 1)
print("====================")

class C { // 外側で弱参照するパターン

    var task: Task<Void, Error>?

    init() {
        print("init")
    }

    func start() {
        print("start before")
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { [weak self] in
            print("start after: \(self)")
            self?.task = Task {
                try await Task.sleep(nanoseconds: NSEC_PER_SEC)
                print("done with self: \(self)")
            }
        }
    }

    deinit {
        print("deinit")
        task?.cancel()
    }
}


autoreleasepool {
    let c = C()
    c.start()

    // startのasyncAfterまで残るように1秒持つ
    DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
        print(c)
    }
}

// init
// start before
// start after: Optional(__lldb_expr_91.C)
// __lldb_expr_91.C
// deinit