但是,当我阅读以下代码行时：
// in Loginviewmodel.swift
init() {
isValid = Observable.combineLatest(username.asObservable(),password.asObservable()) { (username,password) in
return !username.isEmpty && !password.isEmpty
}
}
// in LoginViewController.swift
viewmodel.isValid.bind(to: loginButton.rx.isEnabled).disposed(by: disposeBag)
我很困惑,为什么在不调用subscribe方法的情况下能够观察到isValid Observable？为什么我们可以在LoginViewController.swift中调用bind(to :)而不调用viewmodel.isValid.subscribe(…)之类的东西
public func bind<O: ObserverType>(to observer: O) -> disposable where O.E == E {
return self.subscribe(observer)
}
订阅在里面调用.
关于你的陈述
As far as I kNow,observable won’t produce value unless a observer subscribed on it
这只适用于寒冷的观察者.让我引用这个site
When does an Observable begin emitting its sequence of items? It depends on the Observable. A “hot” Observable may begin emitting items as soon as it is created,and so any observer who later subscribes to that Observable may start observing the sequence somewhere in the middle. A “cold” Observable,on the other hand,waits until an observer subscribes to it before it begins to emit items,and so such an observer is guaranteed to see the whole sequence from the beginning.