Unity custom trigger event

Question

I'm new to Unity

I have multiple objects(all sharing same script) in scene and the player object(own script).

I want to implement custom listener who will inform player every time when single object do some action ( lets say some int value is 10 )

Can someone give me tip for this.

Thanks

Alon Eitan · Accepted Answer · 2020-08-26 05:15:43Z

3

I'd recommend using delegates and events. Have the event fire a function that calls a function in your player script.

(From the link)

EventManager

using UnityEngine;
using System.Collections;

public class EventManager : MonoBehaviour 
{
    public delegate void ClickAction();
    public static event ClickAction OnClicked;

    
    void OnGUI()
    {
        if(GUI.Button(new Rect(Screen.width / 2 - 50, 5, 100, 30), "Click"))
        {
            if(OnClicked != null)
                OnClicked();
        }
    }
}

TeleportScript (using the event from the EventManager)

using UnityEngine;
using System.Collections;

public class TeleportScript : MonoBehaviour 
{
    void OnEnable()
    {
        EventManager.OnClicked += Teleport;
    }
    
    
    void OnDisable()
    {
        EventManager.OnClicked -= Teleport;
    }
    
    
    void Teleport()
    {
        Vector3 pos = transform.position;
        pos.y = Random.Range(1.0f, 3.0f);
        transform.position = pos;
    }
}

edited Aug 26, 2020 at 5:15

Alon Eitan

12k8 gold badges51 silver badges61 bronze badges

answered Aug 14, 2018 at 8:36

user6401627

Sign up to request clarification or add additional context in comments.

2 Comments

Jovan Over a year ago

thanks for answer, I need to pass as parameter gameobject who send this event. is good practice to pass parameter in delegate and Teleport ?

user6401627 Over a year ago

Yes, should be fine.

Everts · Accepted Answer · 2018-08-14 08:59:08Z

You indeed want to use event so that any entity can broadcast info to any others:

public class BroadcastingEntity : MonoBehaviour
{
     public static event Action<BroadcastingEntity> RaiseLowHealth,
     protected void OnLowHealth()
     {
          if(RaiseLowHealth != null) { RaiseLowHealth(this); }
     }
     public static event Action<BroadcastingEntity> RaiseDeath,
     protected void OnDeath()
     {
          if(RaiseDeath!= null) { RaiseDeath(this); }
     }
}

then you have the actual entity:

public class Entity : BroadcastingEntity
{
    private int health = 50;
    public int Health
    {
        get{ return this.health; }
        set
        {
             this.health += value;
             if(this.health <= 0) 
             { 
                 OnDeath(this); 
                 return;
             }
             if(this.health < 10) { OnLowHealth(this); } 
        }
    }
}

finally, you'd have a centralized system to listen to that, let's say your player.

public class Player : MonoBehaviour
{
    void Start()
    {
         BroadcastingEntity.RaiseLowHealth += EntityLowHealth;
         BroadcastingEntity.RaiseDeath += EntityDeath;
    }
    void OnDestroy()
    {
         BroadcastingEntity.RaiseLowHealth -= EntityLowHealth;
         BroadcastingEntity.RaiseDeath -= EntityDeath;
    }
    private void EntityLowHealth(BroadcastingEntity entity){ }
    private void EntityDeath(BroadcastingEntity entity){ }
}

The event is static but the parameter is a reference to the entity that triggers the event. So you can print name or get some other component on it. You can do :

    private void EntityLowHealth(BroadcastingEntity entity)
    {
         print(entity.GetType());
    }

this will give the actual subtype of the entity, so you can perform all kind of actions

Collectives™ on Stack Overflow

Unity custom trigger event

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related