Delegate Example

using UnityEngine;
using System.Collections;

public class DelegateExample : MonoBehaviour {
    //the "method templates" that are used
    public delegate void enterCombatEvent();
    public delegate void exitCombatEvent();
    //the listeners for the events
    public static enterCombatEvent OnEnterCombat;
    public static exitCombatEvent OnExitCombat;

    private bool isInCombat;

    //Call this method when the player encounters an enemy
    public void EnterCombat() {
        isInCombat = true;

        //call the method, all scripts that have a listener will be called
        OnEnterCombat?.Invoke();
    }

    //Call this method when there are no more enemies
    public void ExitCombat() {
        isInCombat = false;

        //call the method, all scripts that have a listener will be called
        OnExitCombat?.Invoke();
    }
}




public class OtherScript : MonoBehaviour {

    // Use this for initialization
    void Start () {
        DelegateExample.OnEnterCombat += CombatStart;
        DelegateExample.OnExitCombat += CombatEnd;
    }
    void OnDestroy() {
        DelegateExample.OnEnterCombat -= CombatStart;
        DelegateExample.OnExitCombat -= CombatEnd;
    }

    //this is called when the player enteres combat
    void CombatStart () {
        //start combat music
    }

    //this is called when the player leaves combat
    void CombatEnd () {
        //start casual music
    }
}