How to add custom static methods to an existing c# struct?

Question

I'm using Unity and Vector struct.

I use Vector3.Distance(a, b) function a lot, but I've just noticed that I want a slightly modified version of it which ignores the Y component and gives the distance in horizontal space. Lets call it a Vector3.HorizontalDistance(a, b).

float distance = Vector3.Distance(position1, position2);
float horizontalDistance = Vector3.HorizontalDistance(position1, position2); //I want this 

The horizontal distance method should look like this

public static float HorizontalDistance(Vector3 pos1, Vector3 pos2)
{
    pos1.y = 0f;
    pos2.y = 0f;

    return Vector3.Distance(pos1, pos2);
}

Right now I put this method in my Utils class and call it like this

float distance = Utils.HorizontalDistance(position1, position2);

But it doesn't feel right, it seems out of context without Vector3 name in in, I want to extend the Vector3's functionality and call it like this

Vector3.HorizontalDistance(a, b);

BUT I don't know how to do that, I couldn't find any information on this subject.?

Answer 1

You can't directly add code to the Vector3 struct, but you can write an extension method. That's the best option for you to have clean code.

void Main()
{
    var p1 = new Vector3() { X = 2f, Y = 1f };
    var p2 = new Vector3() { X = 7f, Y = 3f };
    
    Console.WriteLine(p1.HorizontalDistance(p2));
}

public static class Ext
{
    public static float HorizontalDistance(this Vector3 pos1, Vector3 pos2)
    {
        pos1.Y = 0f;
        pos2.Y = 0f;

        return Vector3.Distance(pos1, pos2);
    }
}