Delegate an event

Question

Hi everyone, I am new at Unity and want to learn the delegate event, but I have a problem. I want when the button has been clicked, it will show some GUI button on it. I already tried the delegate, but the event is not fired (I mean the GUI button is not shown).

Here is the code that I am using:

The code below is to show the GUI button when I run the game.

 public class IItemDatabase : MonoBehaviour
 {
     public delegate void Action(); // Set the event for the button
 
     public static event Action onClicked; // The event for when the button has been clicked
 
     protected virtual void OnGUI()
     {
         // Call the SetStyle method
         SetStyle();
 
         // Set the GUIContent as the tooltip
         GUIContent buttonText = new GUIContent("Open Shop");
 
         // Set the GUIContent as the tooltip
         GUIContent buttonTexts = new GUIContent("Open Inventory");
 
         // T$$anonymous$$s GUILayoutUtility is useful because it is to fit the content
         Rect buttonGUI = GUILayoutUtility.GetRect(buttonText, "Button");
 
         // T$$anonymous$$s GUILayoutUtility is useful because it is to fit the content
         Rect buttonGUIs = GUILayoutUtility.GetRect(buttonTexts, "Button");
 
         // Set where have to the Rect displayed
         buttonGUI.x = 5;
         buttonGUI.y = Screen.height - 25;
 
         // Set where have to the Rect displayed
         buttonGUIs.x = 125;
         buttonGUIs.y = Screen.height - 25;
 
         // If the button has been clicked
 
         if (GUI.Button(buttonGUI, buttonText, style))
         {
             if (onClicked != null)
             {
                 onClicked();
             }
         }
 
         if (GUI.Button(buttonGUIs, buttonTexts, style))
         {
             if (onClicked != null)
             {
                 onClicked();
             }
         }
 
         // End of the clicked button event
     }
 }

And here is the I want it to display when the button has been clicked:

 public class IInventory : MonoBehaviour 
 {
 
     protected virtual void OnEnable()
     {
         IItemDatabase.onClicked += DoGUI;
     }
 
     protected virtual void OnDisable()
     {
         IItemDatabase.onClicked -= DoGUI;
     }
 
     protected virtual void DoGUI()
     {
        Rect slotRect = new Rect(x * 35 + (Screen.width / 3) + 50, y * 35 + (Screen.height / 3) - 10, 30, 30);
                 GUI.Box(slotRect, GUIContent.none);
     }
 }

But when I clicked the button that it suppose to fired the DoGUI() in IInventory class, it does not run the function.

How do I solve t$$anonymous$$s?

Thank you.

Your answer much appreciated!

Answer 1

Best Answer

Answer by vexe · May 11, 2014 at 12:19 PM

I'm always happy to see questions about delegates :)

You seem to have the idea that a delegate and event are different t$$anonymous$$ngs. An event is a delegate - only difference event has is there is an added layer of abstraction and security that makes it impossible to set the delegate value directly, instead you're only allowed to add/remove methods. In other words, with delegates it is possible to do: do myDel = value; and myDel X= value; (where X: - or +) But with events only myEvent X= value; is allowed (where X: - or +) A lot of times, the terms "event" and "delegate" are used interchangeably.

public delegate void Action(); // Set the event for the button

There's already a built-in delegate called Action for you in that exact signature (in the System namespace)

I ran your scripts and they worked fine. DoGUI did get executed.

I like what you're doing - You're following the single responsibility principle by indirectly having your buttons reference the inventory by using delegates - because it's not the button's responsibility to determine what happens in an inventory +1 However; I'm not very fond of the delegate being static. I suggest the following change of design: Create a Slot class that has an Item (if you wish) - The inventory will then have an aggregate (list) of Slots - Each Slot has an onClick - When the inventory creates a slot for ex, it subscribes itself to the slot's onClick so that when a slot/button is clicked, it indirectly notifies the inventory. No need for statics.

More delegate stuff:

If you want to learn everyt$$anonymous$$ng about delegates (Actions, Funcs, Predicates, Anonymous methods, lamda expression, etc) and how they work, Jamie King is the best source.
See t$$anonymous$$s answer here on how to make delegates survive an assembly reload.
For a full solution on serializable/inspectable delegate, see my uFAction.

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Fuhans Puji Saputra · May 11, 2014 at 12:33 PM 0

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vexe · May 11, 2014 at 12:42 PM 0

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Fuhans Puji Saputra · May 11, 2014 at 05:11 PM 0

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vexe · May 11, 2014 at 05:39 PM 0

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Fuhans Puji Saputra · May 11, 2014 at 05:57 PM 0

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Answer 2

Answer by meat5000 · May 11, 2014 at 11:36 AM

I don't do C# but don't you need to add the brackets to call a function?

DoGUI();

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vexe · May 11, 2014 at 01:01 PM 1

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meat5000 ♦ · May 11, 2014 at 01:41 PM 1

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Delegate an event

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