Am I using OnEnable() correctly here?

Question

I have read that OnEnable() should really only be used to initialize the GameObject itself, and to add listeners and such, but it shouldn't be used if you need to access other GameObjects or cache references to external components. With that said, Awake() and Start() only get called once, where OnEnable() gets called everytime the GameObject gets instantiated/created/enabled and such.

Here's my code below...I used OnEnable() to self-register t$$anonymous$$s GameObject to a Managers GameObject, so it needs to happen whenever the GameObject becomes available, hence why it's in OnEnable(). Is t$$anonymous$$s a bad use of OnEnable(), and if yes, can someone show me a better way of doing the same t$$anonymous$$ng? Thanks guys!

     public GameObject menuGameObject;
     public GUITexture menuGUITexture;
     
     public static bool isPauseOn = false;
     
     
     void OnEnable( )
     {
         menuGameObject = menuGameObject != null ? menuGameObject : gameObject.FindC$$anonymous$$ld( "menu", true );        // Just in case it wasn't setup already
         menuGUITexture = menuGUITexture != null ? menuGUITexture : menuGameObject.GetComponent<GUITexture>();    // Same as above
         
         Debug.Log("Self registering t$$anonymous$$s GameObject now");
         Managers.HUDManager.SetHUDElement( HUDSettings.HUDType.MENU, menuGameObject, HUDSettings.ShowMenuHUD );
     }

Answer 1

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Answer by Seth-Bergman · Nov 13, 2012 at 06:19 AM

maybe what you read was referring to the fact that OnEnable can't be a coroutine.. Or, that you shouldn't use OnEnable for cac$$anonymous$$ng objects w$$anonymous$$ch only need to be cached once.. For example, move these lines to function Awake():

 menuGameObject = menuGameObject != null ? menuGameObject : gameObject.FindC$$anonymous$$ld( "menu", true );
 menuGUITexture = menuGUITexture != null ? menuGUITexture : menuGameObject.GetComponent<GUITexture>();

once you store these references the first time, why do you need to re-store them the next time you enable the script? Just call t$$anonymous$$s once in Awake, and they are stored, no need to keep re-initializing the same t$$anonymous$$ng...

NOTE: when you create a new instance of an object, the Start and Awake methods DO RUN. That is, in fact, precisely WHEN they run, when they are first created.

So, all you should have in OnEnable is the one line:

 Managers.HUDManager.SetHUDElement( HUDSettings.HUDType.MENU, menuGameObject, HUDSettings.ShowMenuHUD );

t$$anonymous$$s is perfectly acceptable

but you may also need a corresponding line in method "OnDisable", to unregister it..

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Seth-Bergman · Nov 13, 2012 at 07:04 AM 0

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of course, this is only necessary if you are DISABLING the script or object at some point, then re-enabling it.. if you are just trying to add the object when it is first INSTANTIATED, you have no need for OnEnable at all, Awake() would do it all..

ronronmx · Nov 13, 2012 at 08:19 AM 0

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Hey Seth, thanks for the quick answer! I didn't even think about the fact that those 2 lines would get re-cached every-time OnEnable() is called...thx for the tip, makes lots of sense :)

I am not disabling the script, but the GameObject itself, so the reference cached only gets unregistered in OnApplicationQuit(), so I guess you are right, I might not need OnEnable() after all...

Seth-Bergman · Nov 13, 2012 at 09:14 AM 0

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if you are disabling/re-enabling the GameObject (i.e.: gameObject.enabled = false)

then OnEnable MAY make sense.. it runs when BOTH (script AND GameObject) become true/enabled..

the question is, does the item in question NEED to be re-initialized.. should be easy enough to figure out either way through experimentation (if you're not sure), just see if moving the line under investigation into void Start() breaks stuff :)

ronronmx · Nov 13, 2012 at 11:02 PM 0

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Ah got ya, thanks for clearing that up.

After thinking about this a little bit, I figured that no, it doesn't need to be re-initialized every time, just on setup.

Thanks for the help Seth!

Am I using OnEnable() correctly here?

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