我在Rx
Swift的示例代码中读取了双向绑定运算符.
func <-> <T>(property: ControlProperty<T>,variable: Variable<T>) -> Disposable {
let bindToUIDisposable = variable.asObservable()
.bindTo(property)
let bindToVariable = property
.subscribe(onNext: { n in
variable.value = n
},onCompleted: {
bindToUIDisposable.dispose()
})
return StableCompositeDisposable.create(bindToUIDisposable,bindToVariable)
}
解决方法
感谢提出问题,我花了一些时间来挖掘ControlProperty实现(注意我已经添加了一个.debug()调用来跟踪为控件属性生成的值).
public struct ControlProperty<PropertyType> : ControlPropertyType {
public typealias E = PropertyType
let _values: Observable<PropertyType>
let _valueSink: AnyObserver<PropertyType>
public init<V: ObservableType,S: ObserverType where E == V.E,E == S.E>(values: V,valueSink: S) {
_values = values.debug("Control property values").subscribeOn(ConcurrentMainScheduler.instance)
_valueSink = valueSink.asObserver()
}
public func on(event: Event<E>) {
switch event {
case .Error(let error):
bindingErrorToInterface(error)
case .Next:
_valueSink.on(event)
case .Completed:
_valueSink.on(event)
}
}
}
我的测试设置如下,我删除了所有定位在这里以缩短它：
import UIKit
import RxSwift
import RxCocoa
class ViewController: UIViewController {
let variable = Variable<Bool>(false);
let bag = DisposeBag();
override func loadView() {
super.loadView()
let aSwitch = UISwitch();
view.addSubview(aSwitch)
(aSwitch.rx_value <-> variable).addDisposableTo(bag);
let button = UIButton();
button.rx_tap.subscribeNext { [weak self] in
self?.variable.value = true;
}.addDisposableTo(bag)
view.addSubview(button);
}
}
infix operator <-> {
}
func <-> <T>(property: ControlProperty<T>,variable: Variable<T>) -> Disposable{
let bindToUIDisposable = variable.asObservable().debug("Variable values in bind")
.bindTo(property)
let bindToVariable = property
.debug("Property values in bind")
.subscribe(onNext: { n in
variable.value = n
},onCompleted: {
bindToUIDisposable.dispose()
})
return StableCompositeDisposable.create(bindToUIDisposable,bindToVariable)
}
现在结果.首先我们尝试点击按钮,该按钮应该将变量设置为true.这将在ControlProperty上触发(事件：事件< E>)并将开关值设置为true.
2016-05-28 12:24:33.229: Variable values in bind -> Event Next(true) // value flow value assigned to Variable -> Variable emits event -> ControlProperty receives event -> value assigned to underlying control property (e.g. `on` for `UISwitch`)
接下来让我们触发开关.正如我们所看到的,控件生成一个事件,作为UIControlEventValueChanged的结果,它通过ControlProperty上的_values传递,然后将其值分配给Variable值,如上例所示.但是没有循环,因为更新到Variable值不会触发交换机上的控制事件.
2016-05-28 12:29:01.957: Control property values -> Event Next(false) 2016-05-28 12:29:01.957: Property values in bind -> Event Next(false) 2016-05-28 12:29:01.958: Variable values in bind -> Event Next(false) // value flow trigger the state of control (e.g. `UISwitch`) -> ControlProperty emits event -> value assigned to Variable -> Variable emits event -> ControlProperty receives event -> value assigned to underlying control property (e.g. `on` for `UISwitch`)
所以一个简单的解释是：
>一旦触发某种UIControlEvent,就会发出控件的值
>当值直接分配给控件属性时,控件不会触发更改事件,因此没有循环.
希望它有所帮助,抱歉有点凌乱的解释 – 我通过实验找到了它)
