RxSwift探究的TextField的内部实现序列

RxSwift中的textFiled的使用

let textFiled = UITextField()
textFiled.frame = CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: 300, height: 200))
textFiled.backgroundColor = UIColor.red
self.view.addSubview(textFiled)
   
let _ = textFiled.rx.text.subscribe(onNext: { (content) in
  if let tmpString = content{
      print("收到消息 -------" + tmpString)
  }
}, onError: { (error) in
  print("\(error)")
}, onCompleted: {
  print("completed ...")
}) {
  print("disposed...")
}

在我们的程序启动后，我们就收到一次订阅，这是为什么，在哪里触发一次消息发送，先对这个时间进行探究，从.text进入RxSwift中的UItextFieid+RxSwift.swift我们看到了对应的代码实现，如下

extension Reactive where Base: UITextField {
    /// Reactive wrapper for `text` property.
    public var text: ControlProperty<String?> {
        return value
    }
    
    /// Reactive wrapper for `text` property.
    public var value: ControlProperty<String?> {
        return base.rx.controlPropertyWithDefaultEvents(
            getter: { textField in
                textField.text
            },
            setter: { textField, value in
                // This check is important because setting text value always clears control state
                // including marked text selection which is imporant for proper input 
                // when IME input method is used.
                if textField.text != value {
                    textField.text = value
                }
            }
        )
    }
    // 省略其他代码
    // ....
}

代码分析 我们使用的text属性是继承自ControlProperty结构体的属性，其返回的数据是value，value的getter方法textfield的rx属性的controlPropertyWithDefaultEvents方法，在这个方法中有对应的value值的返回，

代码片1

// 代码片1
internal func controlPropertyWithDefaultEvents<T>(
   editingEvents: UIControlEvents = [.allEditingEvents, .valueChanged],
   getter: @escaping (Base) -> T,
   setter: @escaping (Base, T) -> Void
   ) -> ControlProperty<T> {
   return controlProperty(
       editingEvents: editingEvents,
       getter: getter,
       setter: setter
   )
}

// 代码片2
public func controlProperty<T>(
   editingEvents: UIControlEvents,
   getter: @escaping (Base) -> T,
   setter: @escaping (Base, T) -> Void
) -> ControlProperty<T> {
   let source: Observable<T> = Observable.create { [weak weakControl = base] observer in
           guard let control = weakControl else {
               observer.on(.completed)
               return Disposables.create()
           }

           observer.on(.next(getter(control)))

           let controlTarget = ControlTarget(control: control, controlEvents: editingEvents) { _ in
               if let control = weakControl {
                   observer.on(.next(getter(control)))
               }
           }
           
           return Disposables.create(with: controlTarget.dispose)
       }
       .takeUntil(deallocated)

   let bindingObserver = Binder(base, binding: setter)

   return ControlProperty<T>(values: source, valueSink: bindingObserver)
}

结合这两段代码，代码片1中我们规定了两种事件类型，分别是.allEditingEvents和.valueChanged；

• 在代码片2中创建序列的时，我们可以看到observer.on(.next(getter(control)))这种类型的event它是，订阅了我们UI空间的初始化event;
• let controlTarget = ControlTarget(control: control, controlEvents: editingEvents) {...}这段代码的实现是尾随的逃逸闭包，下面我来看内部的实现

  
  	 init(control: Control, controlEvents: UIControlEvents, callback: @escaping Callback) {
          MainScheduler.ensureRunningOnMainThread()
  
  	        self.control = control
  	        self.controlEvents = controlEvents
  	        self.callback = callback
  	
  	        super.init()
  	
  	        control.addTarget(self, action: selector, for: controlEvents)
  	
  	        let method = self.method(for: selector)
  	        if method == nil {
  	            rxFatalError("Can't find method")
  	        }
      }
  
  
  

  代码分析 这里边，其实就是将，UItextField的event类型的触发方法内部绑定到了textField上，这个触发方法就是eventHandler，在其中就会调用callBack,通过这样的方式就订阅到了textfield的所有的触发事件 然后再通过let bindingObserver = Binder(base, binding: setter)将textfield的赋值event将其定义成绑定观察者，最后在最外层subscribe订阅触发对应的event的事件处理

以上代码多有，不正确之处和写的不详细的地方，欢迎大家扶正和批评，谢谢