API improvement: UIControl.AddTarget

[migueldeicaza]

The binding that we provide today to UIControl.AddTarget is hardcoded to one of the potential method signatures. AddTarget nowadays (or maybe always) supported a vaster set of callbacks, and the actual method invoked today depends on the signature of the selector:

https://developer.apple.com/documentation/uikit/uicontrol#1943645

These are:

@IBAction func doSomething()
@IBAction func doSomething(sender: UIButton)
@IBAction func doSomething(sender: UIButton, forEvent event: UIEvent)

Today, we only support the first kind, we would need to extend our API to take delegates that take a <UIControl> and a <UIControl,UIEvent> to handle those scenarios.

Today, a workaround I used was this:

slider.AddTarget (this, new ObjCRuntime.Selector ("slider:event:"), UIControlEvent.ValueChanged);
...
[Export ("slider:event:")]
void SliderMovedEvent (UISlider senderSlider, UIEvent uievent)

[VincentDondain]

@migueldeicaza what about:

slider.ValueChanged += SliderMovedEvent;
...
void SliderMovedEvent (object sender, EventArgs args)

[VincentDondain]

I think the "vaster set of callbacks" is here: https://github.com/xamarin/xamarin-macios/blob/master/src/UIKit/UIControl.cs#L123-L283

[migueldeicaza]

The EventArgs does not contain the payload, in this case the UIEvent.

What you pointed to are convenience events that wire up the handler, but they do not support wiring up a handler that gets the UIEvent as a parameter. The internals for AddTarget only support the first form that I listed.

[VincentDondain]

Ah got it now I see what you mean. Confirmed.