Collider2D.OnCollisionEnter2D(Collision2D)
Description

Sent when an incoming collider makes contact with this object's collider (2D physics only).

Further information about the collision is reported in the Collision 2D parameter passed during the call.

See Also: Collision2D class, OnCollisionExit2D, OnCollisionStay2D.
function OnCollisionEnter2D(coll: Collision2D) {
	if (coll.gameObject.tag == "Enemy")
		coll.gameObject.SendMessage("ApplyDamage", 10);
}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnCollisionEnter2D(Collision2D coll) {
        if (coll.gameObject.tag == "Enemy")
            coll.gameObject.SendMessage("ApplyDamage", 10);
        
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnCollisionEnter2D(coll as Collision2D) as void:
		if coll.gameObject.tag == 'Enemy':
			coll.gameObject.SendMessage('ApplyDamage', 10)