Get event sender in event handler (UnityAction)?

I'm currently writing a custom button group. I need to add event listener when a button dynamically added in my group. And, when a button is clicked, I need to know which is clicked. How can I know the event sender when an event occurs?

 

You can setup your OnClick event to return the button clicked since it is a Monobehaviour

Code (CSharp):

1. void OnClick(Button button)

 

It doesn't use uGui event system

 

Would something like this work?

Code (csharp):

1. for(int i=0; i<5; i++){
2.     Button btn = ((GameObject)Object.Instantiate(btnPrefab)).GetComponent<Button>();
3.     btn.onClick.AddListener(delegate{Callback(btn);});
4. }
5.  
6. void Callback(Button btnPressed){
7.     Debug.Log(btnPressed.gameObject.name + " pressed!");
8. }

 

Yeah, I did come up with this solution. However, I found that if I want to remove the event listener, I have to store all the delegates in a list in order to pass them when I call RemoveListener().

 

This is not always applicable but you may use RemoveAllListeners();

 

You're right. But what if I only want to remove the specific listener?

 

You would have to keep track of your Listeners either way then. If you want to remove a specific Listener only, you'd need some way of telling it which to remove. An additional (if possibly convoluted) way might be to use extension methods, and keep track of your listeners by name inside an extended EventTrigger class. You might end up with something like:

Code (csharp):

1. btn.onClick.AddListener("ListenerName", delegate{Callback(btn);});
2. btn.onClick.RemoveListener("ListenerName");

And then in your overridden AddListener, simply add the delegate to a Dictionary (I forgot what they're called in C#; Hash?)

I would, however, like to state for the record that I do not endorse this specific approach.