Check collision from another object's script

Question

Is ther a way to know what another object is colliding with? I have a bunch of child objects, each with a trigger collider. I want the parent to be able to know which children are colliding with an object. Here is my parent's script:

 foreach (GameObject child in transform) {
     if (child. /* on trigger stay includes an object with tag "taken", */){
         Debug.Log (child.transform.name + " is colliding with taken");
     }
 }

Is there a way to get a list of another object's collisions from script?

Answer 1

Best Answer

Answer by ethestel · Apr 06, 2015 at 03:48 PM

Hello, iterating through all childs on each physics update is not quite optimized. Try notifying parent only when a collision occurs. Try attaching this script to your parent object:

 using UnityEngine;
 
 public class ParentScript : MonoBehaviour {
 
     public void CollisionDetected(ChildScript childScript)
     {
         Debug.Log("child collided");
     }
 
 }

and this one to every child which are colliding

 using UnityEngine;
 
 public class ChildScript : MonoBehaviour {
 
     void OnCollisionEnter(Collision collision)
     {
         transform.parent.GetComponent<ParentScript>().CollisionDetected(this);
     }
 
 }

Please be aware that childs must be nested inside parents transform.

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Wolfdog · Apr 06, 2015 at 05:16 PM 0

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I like this approach best.

Battles2000 · Nov 29, 2017 at 11:32 PM 0

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Hey what do you mean "nested inside"

Answer 2

Answer by 237641 · Apr 06, 2015 at 03:26 PM

 //on child script
 void OnTriggerEnter()
 {
     collided = true;
 }
 //on parent script
 foreach(Gameobject child in transform)
 {
  if (child.collided)
     Debug.Log(child.transform.name + " collided with taken");
 }

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Wolfdog · Apr 06, 2015 at 05:15 PM 0

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Thank you very much.

Answer 3

Answer by meat5000 · May 09, 2016 at 01:35 PM

You can use ref keyword in C# or use GetComponent to pass the reference to the data.

http://answers.unity3d.com/questions/762798/detect-collision-from-a-script-that-not-attached-t.html#answer-763059

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Answer 4

If your child is buried deep within your objects, you can use this instead. As you may have notice, the parent registers their method via delegate to each child, while the child just triggers the said delegate. if you're dealing with multiple colliders, you can also pass multiple children to your parent.

PARENT CLASS

 public class CollisionParent : MonoBehaviour
 {
     [SerializeField]
     public List<CollisionChild> colliders;
 
     // Start is called before the first frame update
     void Start()
     {
         foreach(CollisionChild child in colliders)
         {
             child.collide = onCollide;
         }
     }
 
     void onCollide(Collider collider)
     {
         Debug.Log("Collided");   
     }
 }

CHILD CLASS

 public class CollisionChild : MonoBehaviour
 {
 
     public delegate void Collide(Collider collide);
 
     public Collide collide;
 
     private void OnTriggerEnter(Collider other)
     {
         collide(other);
     }
 
 }

Check collision from another object's script

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