ReactiveCocoa 4 - CocoaActions

Datetime:2016-08-23 01:36:57         Topic:         Share        Original >>
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CocoaAction is a wrapper around Action type that is available in ReactiveCocoa. (Here you can read more about Action ). We use CocoaAction to bind our Actions to GUI controls. Let's see a quick example of how it works.


Let's imagine a situation, where we have we have a UISwitch control. Every time we switch it on or off, we want to change a MutableProperty text value.

var text = MutableProperty<String>("Switch is on")
let switchControl = UISwitch()

First, let's create Action that will take Bool (switch's value) as an input, return String as output and complete without errors.

let switchAction = Action<Bool, String, NoError>({ (isOn) -> SignalProducer<String, NoError> in
  return SignalProducer<String, NoError> { observer, disposable in
    observer.sendNext(isOn ? "Switch is on" : "Switch is off")

We have to wrap this action into CocoaAction that can be bound to UIControl . In order to do this, we have to remember to transform our UISwitch's value to Action's Bool input.

let switchCocoaAction = CocoaAction(switchAction, { (control) -> Bool in
    let control = control as! UISwitch
    return control.on

Now we can bind our CocoaAction to UISwitch's value change event. Remember that we have to keep reference to our switchCocoaAction.

switchControl.addTarget(switchCocoaAction, action: CocoaAction.selector, forControlEvents: .ValueChanged)

Finally, we can observe our values that are generated by executing our action and change our text value. We can do it quickly by using <~ operator that is available in ReactiveCocoa .

text <~ switchAction.values

This article is cross-posted with my my personal blog .