How to use C# events in Unity3D

Question

I've been working with Events for some time with Winforms, but I'm still quite new with Unity stuff. My project is just to get some C# code running on Android so there's no need for a super efficient solution, just a working one.

Event Handler declaration:

public event EventHandler OnShow, OnHide, OnClose;

Event Handler call:

Debug.Log("OnShow");
if (OnShow != null) 
{
Debug.Log("OnShow_Firing");
OnShow(this, new EventArgs()); 
}
else{
Debug.Log("OnShow_empty");
}

Event Handler Added in an other script but the same gameobject

void Awake(){
Debug.Log("Awake");
this.gameObject.GetComponent<windowScript>().OnShow += OnShowCalled;
}
private void OnShowCalled(object o,EventArgs e)
{
Debug.Log("OnShowCalled");
}

My Debug output is following:

"Awake"
"OnShow"
"OnShowFiring"

but "OnShowCalled" is never executed, there're no Exceptions in Unity's console. I tested EventArgs.Empty instead of new EventArgs() as mentioned in the comments with no effect on my problem .

Looking forward for any help.

My guess is that another object is firing than the one you subscribed to. Add information to the log that helps identify the object instance or just add a breakpoint on `Debug.Log("OnShow");` and see which object is actually it is. Btw.: use `EventArgs.Empty` instead of `new EventArgs()`. — Olivier Jacot-Descombes, Aug 18 '16 at 15:10
there's only one Gameobject which in the scene equipped with both scripts, thanks, I'll try `EventArgs.Empty` — leAthlon, Aug 18 '16 at 15:11
Your `this.gameObject.getComponent()` is kind of weirding me out a little bit. Is it possible that you're not subscribing to the object that's calling the `OnShow()`? — Brandon, Aug 18 '16 at 15:12
There is only one game object, but you are subscribing to an event of a scripting component of this game object. — Olivier Jacot-Descombes, Aug 18 '16 at 15:25

score 7 · Accepted Answer · answered Aug 18 '16 at 15:47

First of all check this tutorial : https://unity3d.com/learn/tutorials/topics/scripting/events

I would recommend using event Action. It is easier to use for beginners.

Example :

Class containing events:

public class EventContainer : MonoBehaviour
{
    public event Action<string> OnShow;
    public event Action<string,float> OnHide;
    public event Action<float> OnClose;

    void Show()
    {
        Debug.Log("Time to fire OnShow event");
        if(OnShow != null)
        {
            OnShow("This string will be received by listener as arg");
        }
    }

    void Hide()
    {
        Debug.Log("Time to fire OnHide event");
        if(OnHide != null)
        {
            OnHide ("This string will be received by listener as arg", Time.time);
        }
    }



    void Close()
    {
        Debug.Log("Time to fire OnClose event");
        if(OnClose!= null)
        {
            OnClose(Time.time); // passing float value.
        }
    }
}

Class which handles events of EventContainer class:

public class Listener : MonoBehaviour
{
    public EventContainer containor; // may assign from inspector


    void Awake()
    {
        containor.OnShow += Containor_OnShow;
        containor.OnHide += Containor_OnHide;
        containor.OnClose += Containor_OnClose;
    }

    void Containor_OnShow (string obj)
    {
        Debug.Log("Args from Show : " + obj);
    }

    void Containor_OnHide (string arg1, float arg2)
    {
        Debug.Log("Args from Hide : " + arg1);
        Debug.Log("Container's Hide called at " + arg2);
    }

    void Containor_OnClose (float obj)
    {
        Debug.Log("Container Closed called at : " + obj);
    }

}

score 1 · Answer 2 · answered Aug 18 '16 at 15:22

For debugging purposes add a Tag property to your component. Then initialize with:

var component = this.gameObject.GetComponent<windowScript>();
component.Tag = "foo";
component.OnShow += OnShowCalled;

And change the logging

Debug.Log("OnShow: " + Tag);

and you will see whether you're dealing with the same object.

score -2 · Answer 3 · edited May 23 '17 at 12:00

Not enough reputation, but possible duplicate or related?

Simple event system in Unity

Events in Unity should be using UnityEvent.

Standard C# events don't work as expected since Unity executes code in a different way than vanilla C# (I don't know much about the topic, but I'm sure someone else does).

In addition, Unity uses an Entity Component System. See http://answers.unity3d.com/questions/669643/entity-component-system.html for more information.

How to use C# events in Unity3D

3 Answers3