How to know which child collider triggered in parent?

Question

I have parent object with 3 children. Each children has one collider (BoxColliders actually) marked as triggers each one.

I want to know in a OnTriggerEnter on the parent side which collider was hit.

Similar to this question: How can I determine which Trigger is hit? But for 3D Colliders (not 2d). As you can see in the accepted answer they used Collider2D.IsTouching but it doesn't seem to exist any analogue method for a 3D Collider

If is not possible, what other solutions are there? What would be the recommended way? I would like to avoid the overhead from methods like CompareTag and SendMessage if possible.

http://answers.unity.com/answers/1206114/view.html

Answer 1

You can give the parent class a public method that takes two arguments, a Collider and some form of identification for which child was hit (e.g. a Transform or Vector3 or int id, depending on what layout the children are in). Then, in each child object, give them a script like

using UnityEngine;

public class ChildCollider : MonoBehaviour {
    void OnTriggerEnter(Collider other) {
        transform.parent.gameObject.GetComponent<ParentScript>.OnChildTriggerEntered(other, transform.position);
    }
}

and in the ParentScript script

public void OnChildTriggerEntered(Collider other, Vector3 childPosition) {
    //Do stuff
}