extension methods unintentionally copying argument - vector

Question

I can't get the extension method to work, It will run, but the Vector3 I put into it as an argument is not the same vector I manipulate inside the TurnClockWiseXZ method.
This is the class calling the method.
using UnityEngine;
using System.Collections;
public class PlayerController : MonoBehaviour {
void FixedUpdate () {
Vector3 test = new Vector3(2,0,3);
Debug.Log ("1: "+test);
test.TurnClockWiseXZ();
Debug.Log ("2: "+test);
}
}
This is where I add the Method:
using UnityEngine;
using System.Collections;
public static class ExtendClass {
public static void TurnClockWiseXZ( this Vector3 vector){
float x = vector.z;
float y = vector.y;
float z = -vector.x;
vector.Set(x,y,z);
}
}
This is the debug messages I get:
1: (2.0, 0.0, 3.0)
2: (2.0, 0.0, 3.0)
This is what I want:
1: (2.0, 0.0, 3.0)
2: (3.0, 0.0, -2.0)

Answer 1

Unfortunately, because Vector3 is a struct (and therefore a value type), it is always passed into a method by making a copy of itself (pass by value). For that reason, any modifications inside the extension method are only affecting the copy.
I see a few alternatives.
1) Make your extension method return the new copied vector and reset the outer variable. It would look like this when calling: test = test.TurnClockwiseXZ();
2) Use a static method instead (not an extension method) that returns void, but takes a vector as a ref parameter. So that would look like this: ExtendClass.TurnClockwiseXZ(ref test); And the definition would be public void TurnClockwiseXZ(ref Vector3 vect) This passes the vector by reference, so it modifies the outer variable inside the function.
3) If you are just modifying the position inside a transform most of the time (as I am), then you can have the extension method operate directly on the transform. Because the transform is a class (and not a struct), it is passed by reference by default and the extension method would work. That solution would look like this:
public void TurnClockwiseXZ(this Transform transform) {
float x = transform.position.z;
float y = transform.position.y;
float z = -transform.position.x;
transform.position = new Vector3(x,y,z);
}
And used as: transform.TurnClockwiseXZ();
I personally have extension methods for SetX, SetY, and SetZ on the transform to easily modify the position. Saves some hassle.