Uitextfield and a Uilabel binding analysis

Reprinted from: http://fengdeng.github.io/blog/2016/01/22/rxswift-dao-di-%5B%3F%5D-ge-uitextfieldshi-ru-he-he-%5B%3F% 5d-ge-uilabelbang-ding-de/

Read more and think it over!

As long as one line of code

writeTextField.rx_text.bindTo(displayLabel.rx_text)

Look at the effect

So how is this going to be achieved?

Overall analysis

代码层：writeTextField的rx_text通过bingTo这个函数和displayLabel的rx_text绑定了。Rx思想：一个被观察者(Observable)通过bingTo函数和一个观察者(Observer)绑定了，这样无论被观察这如何变化，观察者都了如指掌

Deep analytic writetextfield.rx_text

This is a observable. is also a observer. Rx_text is an extended property of Rxswift to Uitextfield, on the code

public var rx_text: ControlProperty<String> {    return rx_value(getter: { [weak self] in        self?.text ?? ""    }, setter: { [weak self] value in        self?.text = value    })}

Rx_text is a controlproperty<string> . Generated by the following function. Let's take a look at that function

Func rx_value<t:equatable> (Getter Getter: ()-T, Setter:t-I, Void), controlproperty<t> {Let            source:observable<t> = observable.create {[weak self] observer on guard let control = Self else { Observer.on (. Completed) return nopdisposable.instance} observer.on (. Next (Getter ())) Let Controltarget = Controltarget (Control:control, controlevents: [. Alleditingevents,. ValueChanged]) {control in Observer.on (. Next (Getter ()))} return anonymousdisposable {Controltarget.dispose ()}}. Dist Inctuntilchanged (). Takeuntil (rx_deallocated) return controlproperty<t> (Values:source, Valuesink:anyobse RVer {event in Mainscheduler.ensureexecutingonscheduler () switch event {case. Next (let value): Setter (value) case. Error (let error): Bindingerrortointerface (Error) break case. CompleTed:break}})} 

This function is Uicontrol, and all Uicontrol subclasses have ha. Uitextfield is a subclass of Uicontrol

The function is a little bit long, we analyze it one step at a time, in fact, two sentences

The first sentence, the source generation process. Source is a observable, which is where the observable

1. Get self first, get no direct completed
2. Get it, straight next a getter just passed in. Here is self?.text ?? "" , that flows away a observable
3. Generate a ControlTarget , this ControlTarget whenever ValueChanged will flow away a observable (this ControlTarget a bit more, next talk)
4. After three steps above, here is a observable. For this observable distinctUntilChanged() , this function shows that only a string change will continue to flow down
5. takeUntil(rx_deallocated)Until this Uitextfield is released.
6. Source ends, this process of source is the 5 steps above

In fact, if a Uitextfield rx_text as a observable, the above code is enough.

In order to implement Uitextfield can also be used as observer, so the following code.

The second sentence, through source, generates one ControlProperty<String> . The observer is the type to be returned by this function. It is both a observer and a observable

1. ControlProperty<PropertyType>the initialization method of a direct call is generated

2. Look at a closure that the initialization method brings in.

    AnyObserver { event in     MainScheduler.ensureExecutingOnScheduler()     switch event {     case .Next(let value):         setter(value)     case .Error(let error):         bindingErrorToInterface(error)         break     case .Completed:         break     }

Because UI actions must be in the main thread. MainScheduler.ensureExecutingOnScheduler()this sentence is to determine if the current thread is
The following code is a response that receives a stream when Uitextfield as a observer.

Displaylabel.rx_text

This is a observer rx_text is an extended property of Rxswift to Uilabel, on the code

public var rx_text: AnyObserver<String> {    return AnyObserver { [weak self] event in        MainScheduler.ensureExecutingOnScheduler()        switch event {        case .Next(let value):            self?.text = value        case .Error(let error):            bindingErrorToInterface(error)            break        case .Completed:            break        }    }}

Very simple, only the code that responds to the stream. If there is a flow,self?.text = value

Some students may have doubts, Uitextfield can be observed, can also be observers. Uilabel can only be the observer, if I want to observe the text of Uilabel What to do???

Haha, easy,please try KVO

displayLabel.rx_observe(String.self, "text").subscribe { (event) -> Void in        switch event{        case .Next(let m):            print(m)        case .Completed:            print("")        case .Error(let t):            print(t)        }    }

KVO is still relatively simple, we can see for ourselves. Maybe next time I write

BindTo

bingToIs the expansion of observable

public func bindTo<O: ObserverType where O.E == E>(observer: O) -> Disposable {    return self.subscribe(observer)}

Internally called Observable's subscribe method to associate with a observer

This is the subscribe method that calls the Controlproperty.

public func subscribe<O : ObserverType where O.E == E>(observer: O) -> Disposable {    return _values.subscribe(observer)}

_VALUES.SUBSCRIBE (Observer) calls the Subscribe method of the Subscribeon class,

Subscribeon did not implement the Subscribe method, then went to his father class producer to call the

override func subscribe<O : ObserverType where O.E == Element>(observer: O) -> Disposable {    if !CurrentThreadScheduler.isScheduleRequired {        return run(observer)    }    else {        return CurrentThreadScheduler.instance.schedule(()) { _ in            return self.run(observer)        }    }}

Producer again went to its subclass Subscribeon to call the Run method

override func run<O : ObserverType where O.E == Ob.E>(observer: O) -> Disposable {    let sink = SubscribeOnSink(parent: self, observer: observer)    sink.disposable = sink.run()    return sink}

When each value of Uitextfield is generated, the following method is called, in SubscribeOnSink this class

func on(event: Event<Element>) {    forwardOn(event)    if event.isStopEvent {        self.dispose()    }}

forwardOn(event)This method also goes to the SubscribeOnSink parent class of this class to invoke the

final func forwardOn(event: Event<O.E>) {    if disposed {        return    }    _observer.on(event)}

Finally transferred to _observer.on(event) this sentence. is also the method of Uilabel Rx_text, on on(event) is a closure, in Uilabel Rx_text equivalent to the following code

    { [weak self] event in        MainScheduler.ensureExecutingOnScheduler()        switch event {        case .Next(let value):            self?.text = value        case .Error(let error):            bindingErrorToInterface(error)            break        case .Completed:            break        }

The above is a complex inheritance?? Method call. Read more and think it over!

At this point, a complete observable and a observer binding end

Uitextfield and a Uilabel binding analysis