How to get data from wheel collider?

Unity Engine
1

I’m trying to set up a log that prints the rpm of one of the wheel colliders in my vehicle once every frame. I have my code like this:

#pragma strict
var wheel = GetComponent("wheel_bl");

function Update () {
    print(wheel.collider.WheelCollider.rpm);
}

However, Unity gives this error:
BCE0019: ‘WheelCollider’ is not a member of ‘UnityEngine.Collider’.

What am I doing wrong? The Scripting API page says that WheelCollider inherits from Collider, but it isn’t working for me.

2

The Error message tells you exactly what you need to know. While WheelCollider does inherit from Collider, it is not a member of Collider. When you have a Collider object, it has no inherent knowledge of the derived type’s members. The Collider must be downcast to access these members I recommend you review some of the basic OOP concepts.

Here are two solutions:

You could expose a public variable of type WheelCollider, and assign the collider to the script to access the rpm:

public class Example : MonoBehaviour {

    public WheelCollider theWheelColliderOfInterest;

    void YourMethod () {
        Debug.Log(theWheelColliderOfInterest.rpm);
    }
}

Alternatively, you can cast the GameObject’s Collider as a WheelCollider:

[RequireComponent(typeof(WheelCollider))]
public class Example : MonoBehaviour {
    void YourMethod () {
        WheelCollider castCollider =  gameObject.collider as WheelCollider;
        Debug.Log(castCollider.rpm);
    }
}

I recommend the first approach.