MonoBehaviour.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 Collision2D parameter passed during the call. If you don't need this information then you can declare OnCollisionEnter2D without the parameter.

function OnCollisionEnter2D(coll: Collision2D) {
	if (coll.gameObject.tag == "Enemy")
		coll.gameObject.SendMessage("ApplyDamage", 10);
}

using UnityEngine;
using System.Collections;

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

import UnityEngine
import System.Collections

public class ExampleClass(MonoBehaviour):

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