反应性 Cocoa - 然后是自定义信号与 UI 信号

Question

我开始使用 Reactive Cocoa 所以我写了一个小测试看看我是否理解 then 构造。目标是仅在发送某些信号后才将文本从文本字段输出到标签。我试过 rac_signalForControlEvents(UIControlEvents.TouchUpInside) 和非常简单的自定义信号。前者甚至不调用 then 闭包，而后者确实按预期工作。这里有什么问题？

func someSetupFunction()
{
#if true
    // Why does this doesn't work?

    button.rac_signalForControlEvents(UIControlEvents.TouchUpInside).then
        {
            let strongSelf = weakSelf
            return strongSelf?.textField.rac_textSignal()
        }.subscribeNext
        { object in
            let strongSelf = weakSelf
            strongSelf?.label.text = object as! String! + " - 0"
        }
#else
    // ... but this does?

    customSignal().then
        {
            let strongSelf = weakSelf
            return strongSelf?.textField.rac_textSignal()
        }.subscribeNext
        { object in
            let strongSelf = weakSelf
            strongSelf?.label.text = object as! String! + " - 1"
        }
#endif
}

func customSignal() -> RACSignal
{
    return RACSignal.createSignal
        { subscriber in
            subscriber.sendNext(nil)
            subscriber.sendCompleted()
            return nil
        }
}

Answer 1

来自 then 的文档：

Ignores all nexts from the receiver, waits for the receiver to complete, then subscribes to a new signal.

button.rac_signalForControlEvents 没有完成（至少在点击按钮时没有完成），这就是什么都没有发生的原因。

iv-mexx 的原始答案可在 https://github.com/ReactiveCocoa/ReactiveCocoa/issues/2671

找到

反应性 Cocoa - 然后是自定义信号与 UI 信号

Reactive Cocoa - then on custom signal vs UI signal

cocoa-touch

ios

swift

reactive-cocoa-4