C# Extension Methods

Hi Guys,

Is it possible to do C# Extension methods in unity?

What I am trying to do is extend GameObjects - as an example:

Code (csharp):

1.  
2.  
3. using UnityEngine;
4. using System.Collections;
5.  
6. public static class MyExtensions {
7.    
8.     public static void MyExtendedMethod(this GameObject gameObject) {
9.        
10.         // Do something
11.  
12.     }
13. }
14.  
15.  

Code (csharp):

1.  
2.  
3. using UnityEngine;
4. using System.Collections;
5.  
6. public class MyScript : MonoBehaviour {
7.  
8.     void Start () {
9.        
10.         GameObject.MyExtendedMethod();     
11.        
12.     }
13.  
14. }
15.  

Everything seems fine, monodevelop picks up my extended class when I go "GameObject" "." ->MyExtendedMethod() but gives a error message

Code (csharp):

1. error CS0117: `UnityEngine.GameObject' does not contain a definition for `MyExtendedMethod'

Thanks in advance!

 

EDIT: nevermind.

Not sure, maybe Unity doesn't factor those in.

At the very least, you can definitly work around them if they aren't supported.

 

Using a instance of a object works.

Code (csharp):

1. myGameObject.MyExtensionMethod();

Which is great, but I want to also be able to do

Code (csharp):

1. GameObject.MyExtensionMethod();

Any suggestions would be great!

 

Oh woops, completely overlooked that.

Static extension methods do not exist in C# (Unity or otherwise). This is by design.

Your best workaround is to simply create your own custom GameObjectEx class:

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public static class GameObjectEx
6. {
7.     public static void DoSomething(GameObject target)
8.     {
9.         // Do something
10.     }
11.    
12.     public static void DoSomethingElse()
13.     {
14.         // Do something else
15.     }
16. }
17.  
18. //elsewhere
19. GameObjectEx.DoSomething(myGameObject);
20. GameObjectEx.DoSomethingElse();
21.  

 

Sorry I don't quite follow.

I thought extensions have to be static.

Code (csharp):

1. CS1105: `MyExtensions.MyExtensionMethod(this GameObject, string)': Extension methods must be declared static

 

You define them with a "static" keyword, but they are accessed like instance-level methods. Notice the "this GameObject"; it's providing the context of "this". Static methods have no concept of "this"

So it's possible to create an extension method that operates like this:
myGameObjectInstance.MyExtensionMethod();

But it is not possible to create an extension method that operates like this:
GameObject.MyExtensionMethod();

EDIT: there's more information here: http://msdn.microsoft.com/en-us/library/bb383977.aspx
It touches on the static/instance nature of extension methods.

 

Thanks