[Combine] Cancellable과 AnyCancellable

 

viewController가 deinit 될때, 그 안의 Pulisher가 auto-cancel 되는지 실험해봅시다 --! 

5초 후에 이벤트를 발행하는 Publisher와 3초 후에 deinit되는 viewController가 있습니다

 

1) stream을 안담아줄 때 

	class ViewController: UIViewController {
	deinit {
	print("viewController deinit")
	}
	override func viewDidLoad() {
	super.viewDidLoad()
	let stream = Publishers.Just("is Alive?")
	.delay(for: .seconds(5), scheduler: RunLoop.main)
	.sink(receiveCompletion: { (completion) in
	switch completion {
	case .finished: print("finished")
	case .failure(let error): print(error)
	}
	}, receiveValue: {
	print($0)
	})
	DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
	UIApplication.shared.keyWindow?.rootViewController = nil
	}
	}
	<output>
	viewController deinit
	is Alive?
	finished

view raw AnyCancellableTest1.swift hosted with ❤ by GitHub

viewController가 deinit되어도 스트림이 살아있습니다 

 

 

2) stream을 Cancellable에 담아줄 때 

	class ViewController: UIViewController {
	var cancellable: Cancellable?
	deinit {
	print("viewController deinit")
	}
	override func viewDidLoad() {
	super.viewDidLoad()
	let stream = Publishers.Just("is Alive?")
	.delay(for: .seconds(5), scheduler: RunLoop.main)
	.sink(receiveCompletion: { (completion) in
	switch completion {
	case .finished: print("finished")
	case .failure(let error): print(error)
	}
	}, receiveValue: {
	print($0)
	})
	cancellable = stream
	DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
	UIApplication.shared.keyWindow?.rootViewController = nil
	}
	}
	<output>
	viewController deinit
	is Alive?
	finished

view raw AnyCancellableTest2.swift hosted with ❤ by GitHub

viewController가 deinit되어도 여전히 스트림이 살아있습니다 

 

3) stream을 Cancellable에 담아주고 deinit 때 cancel 시켜줄 때 

	class ViewController: UIViewController {
	var cancellable: Cancellable?
	deinit {
	print("viewController deinit")
	cancellable?.cancel()
	}
	override func viewDidLoad() {
	super.viewDidLoad()
	let stream = Publishers.Just("is Alive?")
	.delay(for: .seconds(5), scheduler: RunLoop.main)
	.sink(receiveCompletion: { (completion) in
	switch completion {
	case .finished: print("finished")
	case .failure(let error): print(error)
	}
	}, receiveValue: {
	print($0)
	})
	cancellable = stream
	DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
	UIApplication.shared.keyWindow?.rootViewController = nil
	}
	}
	<output>
	viewController deinit

view raw AnyCancellableTest3.swift hosted with ❤ by GitHub

이렇게 deinit 될때 cancel시키는 코드를 넣어줘야지 스트림이 같이 끝납니다

 

4) stream을 AnyCancellable에 담아줄 때 

	class ViewController: UIViewController {
	var cancellable: AnyCancellable?
	deinit {
	print("viewController deinit")
	}
	override func viewDidLoad() {
	super.viewDidLoad()
	let stream = Publishers.Just("is Alive?")
	.delay(for: .seconds(5), scheduler: RunLoop.main)
	.sink(receiveCompletion: { (completion) in
	switch completion {
	case .finished: print("finished")
	case .failure(let error): print(error)
	}
	}, receiveValue: {
	print($0)
	})
	cancellable = AnyCancellable(stream)
	DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
	UIApplication.shared.keyWindow?.rootViewController = nil
	}
	}
	<output>
	viewController deinit

view raw AnyCancellableTest.swift hosted with ❤ by GitHub

AnyCancellable에 담아줘야지 deinit 될 때 auto-cancel 됩니다 

AnyCancellable로 스트림의 메모리 관리를 해줘야합니다...!! 

 

 

Cancellable과 AnyCancellable이 어떻게 다른 지는  RxSwift vs Combine - 스펙 / 성능 / 개념 비교 이 포스팅에 적어두었구요

왜 이런 차이가 나는 지는 저도 잘 모르겠습니다 😭 누가 좀 알려주세요오... 정말 궁금..