Collision2D.transform

Description

The Transform of the incoming object involved in the collision.

Additional resources: Transform class.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    void OnCollisionEnter2D(Collision2D collision2D)
    {
        //If the object we collided with was an Asteroid.
        if (collision2D.transform.name == "Asteroid")
        {
            //Sets this object as the new parent of the Transform of the object involved in the collision.
            collision2D.transform.SetParent(gameObject.transform);
        }
    }
}