combineLatest test

combineTest.swift

import Cocoa


import Combine

var subscriptions = Set<AnyCancellable>()
func futureIncrement(
    integer: Int,
    afterDelay delay: TimeInterval) -> AnyPublisher<Int, Never> {
    Deferred {
        Future<Int, Never> { promise in
            print("init")
      
            promise(.success(integer + 1))
      
        }
    }.subscribe(on: DispatchQueue.main).eraseToAnyPublisher()
}

let future = futureIncrement(integer: 1, afterDelay: 3)

future
  .sink(receiveCompletion: { print($0) },
        receiveValue: { print($0) })
  .store(in: &subscriptions)


future
  .sink(receiveCompletion: { print("Second", $0) },
        receiveValue: { print("Second", $0) })
  .store(in: &subscriptions)


Just(2).combineLatest(future).sink(receiveCompletion: { print("you won't see me", $0) },
                                  receiveValue: { print("never 1", $0) })
                            .store(in: &subscriptions)

future.combineLatest(Just(2)).sink(receiveCompletion: { print("you won't see me, too", $0) },
                                  receiveValue: { print("never 2", $0) })
                            .store(in: &subscriptions)

/* line 19 */  let future = futureIncrement(integer: 1, afterDelay: 3).share()

Future 是少數幾個 class 的 Publisher，很容易誤會。

delay沒被用到欸，冗余參數？
對combine不熟，不過這看起來跟subscribe(on:)沒關係呀🤔
share就好了，況乎為何要subscribe(on: ?

為何subscribe(on:)會有影響我也不懂哈

Just(2)
    .subscribe(on: DispatchQueue.global())
    .combineLatest(Just(1))
    .sink(
        receiveCompletion: { print("you won't see me", $0) },
        receiveValue: { print("never", $0)
    })
    .store(in: &subscriptions)

這樣寫也不會動，我覺得這是bug