（*useful）标记：目前觉得有用的函数
//FIXME 标记：待补充
Subject：Subject 可以看做是一种代理和桥梁
既可订阅消息，又可以reemitting ，emit new items
extension ObservableType { //封装来方便调用调试的方法
/**
Add observer with `id` and print each emitted event.
- parameter id: an identifier for the subscription.
*/
func addObserver(_ id: String) -> Disposable {
return subscribe { print("Subscription:", id, "Event:", $0) }
}
}
func writeSequenceToConsole<O: ObservableType>(name: String, sequence: O) -> Disposable {
return sequence.subscribe { event in
print("Subscription: \(name), event: \(event)")
}
}
PublishSubject：向所有订阅发广播
：订阅之后才能收到消息
let disposeBag = DisposeBag()
let subject = PublishSubject<String>()
subject.addObserver("1").disposed(by: disposeBag)
subject.onNext("🐶")
subject.onNext("🐱")
subject.addObserver("2").disposed(by: disposeBag)
subject.onNext("🅰️")
subject.onNext("🅱️")
打印：
Subscription: 1 Event: next(🐶)
Subscription: 1 Event: next(🐱)
Subscription: 1 Event: next(🅰️)
Subscription: 2 Event: next(🅰️) // 订阅了才能收到消息，前面的没有收到
Subscription: 1 Event: next(🅱️)
Subscription: 2 Event: next(🅱️)
ReplaySubject：向所有订阅发广播
并向新订阅发送先前事件(bufferSize决定往期个数，类似RACReplaySubject的热信号）。
let disposeBag = DisposeBag()
let subject = ReplaySubject<String>.create(bufferSize: 10)
subject.addObserver("1").disposed(by: disposeBag)
subject.onNext("🐶")
subject.onNext("🐱")
subject.addObserver("2").disposed(by: disposeBag)
subject.onNext("🅰️")
subject.onNext("🅱️")
打印：
Subscription: 1 Event: next(🐶)
Subscription: 1 Event: next(🐱)
Subscription: 2 Event: next(🐶) //这个就是往期发送的消息，
Subscription: 2 Event: next(🐱) //这里bufferSize为10，但emit只有两次
Subscription: 1 Event: next(🅰️)
Subscription: 2 Event: next(🅰️)
Subscription: 1 Event: next(🅱️)
Subscription: 2 Event: next(🅱️)
BehaviorSubject向所有订阅发广播
并向新订阅发送最近的一次emit消息，类似ReplaySubject的bufferSize为1
let disposeBag = DisposeBag()
let subject = BehaviorSubject(value: "🔴")
subject.addObserver("1").disposed(by: disposeBag)
subject.onNext("🐶")
subject.onNext("🐱")
subject.addObserver("2").disposed(by: disposeBag)
subject.onNext("`🅰️`")
subject.onNext("🅱️")
subject.addObserver("3").disposed(by: disposeBag)
subject.onNext("🍐")
subject.onNext("🍊")
打印：
Subscription: 1 Event: next(🔴) //最近的一次emit消息
Subscription: 1 Event: next(🐶)
Subscription: 1 Event: next(🐱)
Subscription: 2 Event: next(🐱) //最近的一次emit消息
Subscription: 1 Event: next(🅰️)
Subscription: 2 Event: next(🅰️)
Subscription: 1 Event: next(🅱️)
Subscription: 2 Event: next(🅱️)
Subscription: 3 Event: next(🅱️) //最近的一次emit消息
Subscription: 1 Event: next(🍐)
Subscription: 2 Event: next(🍐)
Subscription: 3 Event: next(🍐)
Subscription: 1 Event: next(🍊)
Subscription: 2 Event: next(🍊)
Subscription: 3 Event: next(🍊)
