/*
     AsyncSubject 将在源 Observable 产生完成事件后，发出最后一个元素（仅仅只有最后一个元素），如果源 Observable 没有发出任何元素，只有一个完成事件。那 AsyncSubject 也只有一个完成事件。
     它会对随后的观察者发出最终元素。如果源 Observable 因为产生了一个 error 事件而中止， AsyncSubject 就不会发出任何元素，而是将这个 error 事件发送出来。
     */
    func setupAsyncSubject() {
        let subject = AsyncSubject<String>()
        subject
            .subscribe {
                print("AsyncSubject  1 Event :",$0)
            }
            .disposed(by: disposeBag)
        subject.onNext("🐶")
        subject.onNext("🐥")
        subject.onNext("🐍")
        subject.onNext("🐯")
        subject.onCompleted()
    }

AsyncSubject  1 Event : next(🐯)
AsyncSubject  1 Event : completed

/*
     PublishSubject 将对观察者发送订阅后产生的元素，而在订阅前发出的元素将不会发送给观察者。如果你希望观察者接收到所有的元素，你可以通过使用 Observable 的 create 方法来创建 Observable，或者使用 ReplaySubject。
     如果源 Observable 因为产生了一个 error 事件而中止， PublishSubject 就不会发出任何元素，而是将这个 error 事件发送出来。
     */
    func setupPublishSubject() {
        let subject = PublishSubject<String>()
        subject
            .subscribe {print("PublishSubject  1 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🐶")
        subject.onNext("🐥")
        subject
            .subscribe {print("PublishSubject  2 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🐍")
        subject.onNext("🐯")
        subject.onCompleted()
    }

PublishSubject  1 Event:  next(🐶)
PublishSubject  1 Event:  next(🐥)
PublishSubject  1 Event:  next(🐍)
PublishSubject  2 Event:  next(🐍)
PublishSubject  1 Event:  next(🐯)
PublishSubject  2 Event:  next(🐯)
PublishSubject  1 Event:  completed
PublishSubject  2 Event:  completed

/*
     ReplaySubject 将对观察者发送全部的元素，无论观察者是何时进行订阅的。
     这里存在多个版本的 ReplaySubject，有的只会将最新的 n 个元素发送给观察者，有的只会将限制时间段内最新的元素发送给观察者。
     如果把 ReplaySubject 当作观察者来使用，注意不要在多个线程调用 onNext, onError 或 onCompleted。这样会导致无序调用，将造成意想不到的结果。
     */
    func setupReplaySubject() {
        /// Creates new instance of `ReplaySubject` that replays at most `bufferSize` last elements of sequence.
        ///
        /// - parameter bufferSize: Maximal number of elements to replay to observer after subscription.
        /// - returns: New instance of replay subject.
        let subject = ReplaySubject<String>.create(bufferSize: 1)
        subject
            .subscribe{print("ReplaySubject  1 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🐶")
        subject.onNext("🐥")
        subject
            .subscribe{ print("ReplaySubject  2 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🐍")
        subject.onNext("🐯")
    }

ReplaySubject  1 Event:  next(🐶)
ReplaySubject  1 Event:  next(🐥)
ReplaySubject  2 Event:  next(🐥)
ReplaySubject  1 Event:  next(🐍)
ReplaySubject  2 Event:  next(🐍)
ReplaySubject  1 Event:  next(🐯)
ReplaySubject  2 Event:  next(🐯)

/*
     当观察者对 BehaviorSubject 进行订阅时，它会将源 Observable 中最新的元素发送出来（如果不存在最新的元素，就发出默认元素）。然后将随后产生的元素发送出来。
     如果源 Observable 因为产生了一个 error 事件而中止， BehaviorSubject 就不会发出任何元素，而是将这个 error 事件发送出来。
     */
    func setupBehavioreSubject() {
        let subject = BehaviorSubject(value: "🏀")
        subject
            .subscribe{ print("BehaviorSubject 1 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🐶")
        subject.onNext("🐥")
        subject
            .subscribe{ print("BehaviorSubject 2 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🅰️")
        subject.onNext("🅱️")
        subject
            .subscribe{ print("BehaviorSubject 3 Event: ", $0)}
            .disposed(by: disposeBag)
        subject.onNext("🍎")
        subject.onNext("🍐")
    }

BehaviorSubject 1 Event:  next(🏀)
BehaviorSubject 1 Event:  next(🐶)
BehaviorSubject 1 Event:  next(🐥)
BehaviorSubject 2 Event:  next(🐥)
BehaviorSubject 1 Event:  next(🅰️)
BehaviorSubject 2 Event:  next(🅰️)
BehaviorSubject 1 Event:  next(🅱️)
BehaviorSubject 2 Event:  next(🅱️)
BehaviorSubject 3 Event:  next(🅱️)
BehaviorSubject 1 Event:  next(🍎)
BehaviorSubject 2 Event:  next(🍎)
BehaviorSubject 3 Event:  next(🍎)
BehaviorSubject 1 Event:  next(🍐)
BehaviorSubject 2 Event:  next(🍐)
BehaviorSubject 3 Event:  next(🍐)