Unityaction vs Method

Questions & Answers
1

I’m still pretty new to certain subjects of unity, so I don’t know if this is a stupid question. XD

I tried to find information on this subject but I couldn’t find anything specific.
Currently I’m learning to create dynamic menus.
To handle the variable processes started by buttons I’m working with unityactions.
However, there’s something I don’t understand.

When adding listeners to an onclick event for example it doesn’t seem to make a difference if I’m passing a unityaction or just simply the name of a method.

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.Events;
using System.Collections;

public class test_unityaction : MonoBehaviour {

	private UnityAction action;

	void Awake() {
		action = new UnityAction (Func);
		gameObject.GetComponent<Button> ().onClick.AddListener (action);
		gameObject.GetComponent<Button> ().onClick.AddListener (Func);
	}

	void Func() {
		print ("Func");
	}

}

This is a very basic and easy code example.
Add it to a button to test it.

The function is launched twice.

So my question is what is the difference here?
Why should I pass a unityaction if I can simply pass the method name?
Passing the method directly instead of a unityaction makes the code much more simple.
Is there a disadvantage for passing the method directly because it seems to work as intended?

2

I have never used UnityActions. I read in the doc that it is a delegate. Then, you could possibly do something like this (didn’t tested)

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.Events;
using System.Collections;

public class test_unityaction : MonoBehaviour {

    private UnityAction action;

    void Awake() {
        action = new UnityAction (Func);
        action += Func1 ;
        action += Func2 ;
        gameObject.GetComponent<Button> ().onClick.AddListener (action);
    }

    void Func() {
        print ("Func");
    }

    void Func1() {
        print ("Func1");
    }

    void Func2() {
        print ("Func2");
    }

    void Func3() {
        print ("Func3");
    }
}

Obviously, using UnityAction is clearer.

You could also modify the function called dynamically with something like this :

    void Update() {
        if (Input.GetKeyDown("space"))
        {
            gameObject.GetComponent<Button> ().onClick.RemoveListener( action ) ;
            action -= Func1 ;
            action += Func3 ;
            gameObject.GetComponent<Button> ().onClick.AddListener (action);
        }
    }

Then, your button won’t call Func1 anymore but call Func3 instead when you click on your button.

EDIT : I have tested without removing and adding back again the action, it doesn’t seem to work.

Everything I did could have been possible without the UnityAction. Just remove the function you don’t want anymore and add the one you want.

By the way, since AddListener is wainting for a delegate without any parameter and a return type of void, you could have done this :

gameObject.GetComponent<Button> ().onClick.AddListener ( delegate()
    {
        Debug.Log("Hello World !") ;
    }
)

Or, with anonymous delegate :

gameObject.GetComponent<Button> ().onClick.AddListener ( () =>
    {
        Debug.Log("Hello World !") ;
    }
)