官方文档原话:
AnyCancellable
A type-erasing cancellable object that executes a provided closure when canceled.
Subscriber implementations can use this type to provide a “cancellation token” that makes it possible for a caller to cancel a publisher, but not to use the Subscription object to request items.
An Cancellable instance automatically calls when deinitialized.
测试：
import UIKit
import Combine
let subject = CurrentValueSubject<Int, Never>(0)
var testAutoCancel = {
//出了作用域时自动取消订阅
var subsA = subject.sink { (value) in
print("subsA: \(value)")
}
subject.send(1)
}
testAutoCancel()
subject.send(2)
//手动取消订阅后，不再收到element
var subsB = subject.sink { (value) in
print("subsB: \(value)")
}
class Subs {
var subsD: AnyCancellable?
var subsE = AnySubscriber<Int, Never>()
init() {
//出了作用域时自动取消订阅
subject.sink { (value) in
print("subsC: \(value)")
}
//Subs对象销毁时自动取消订阅
subsD = subject.sink(receiveValue: { (value) in
print("subsD: \(value)")
})
subject.receive(subscriber: subsE)
}
}
var subs: Subs? = Subs()
subject.send(3)
subsB.cancel()
subs = nil
subject.send(4)
打印：
subsA: 0
subsA: 1
subsB: 2
subsC: 2
subsD: 2
subsB: 3
subsD: 3
