RxSwift 操作符 (connect & publish)

connect & publish

ReactiveX:
connect: instruct a connectable Observable to begin emitting items to its subscribers
publish: convert an ordinary Observable into a connectable Observable

publish要和connect一起使用才能有效果。当一个被观察者被publish后，它被订阅也是不能收到消息的，只有它被connect操作符连接后，才能收到数据。

let ob = Observable<Int>.just(1).publish()
ob.subscribe(onNext: { int in
    print("element: ", int)
}).disposed(by: bag)

Observable<Int>
    .timer(3, scheduler: MainScheduler.instance)
    .subscribe(onNext: { [weak self] _ in
        guard let this = self else { return }
        ob.connect().disposed(by: this.bag)
    })
    .disposed(by: bag)

2s后输出：
element: 1