Question regarding Delegates & Events

Questions & Answers
1

Hello

I am trying to learn the subject of Delegates and events in unity.

I have seen this example on:

The examples there are quite good and simple to understand so i followed it…

in the delegate/events it uses the following example:

public class Clicker : MonoBehaviour 
{
  // Event Handler
  public delegate void OnClickEvent(GameObject g);
  public event OnClickEvent OnClick;
  
  // Handle our Ray and Hit
  void Update () 
  {
    // Ray
    Ray ray = Camera.mainCamera.ScreenPointToRay(Input.mousePosition);
    
    // Raycast Hit
    RaycastHit hit;
    
    if (Physics.Raycast(ray, out hit, 100))
    {
      // If we click it
      if (Input.GetMouseButtonUp(0))
      {
        // Notify of the event!
                         OnClick(hit.transform.gameObject);
      }
    }
  }
}

And now to reference the delegate from our other scripts that are listening to the call:
Other script:

public class GoldPile : MonoBehaviour 
{
  // Awake
  void Awake ()
  {
    // Start the event listener
    Clicker.Instance.OnClick += OnClick;
  }
  
  // The event that gets called
  void OnClick(GameObject g)
  {
    // If g is THIS gameObject
    if (g == gameObject)
    {
      Debug.Log("Hide and give us money!");
      
      // Hide
      gameObject.active = false;
    }
  }
}

Now, what i am asking?
It seems to be that if you have like 100 GoldPile Scripts attached to objects.
Everytime i “GetMouseButtonUP(0)” it will call 100 times the 100 scripts (since u have 100 objects of GolePile) to check if its a GoldPile gameobject. it seems to be inefficient and could cause slowdowns if you have like 1,000 GoldPiles.

I want to learn Delegates & Events, but i also want to learn how to use them the right way.

I would love to learn from your experience.

2

Subscribe in OnEnable and unsubscribe in OnDisable. Failure to do so can and will cause memory leaks.

void OnEnable() { foo += bar; }
void OnDisable() { foo -= bar; }

To answer your question; I would not recommend using an event system like this in such situations. It’s overkill. Any situation which creates 999 wasted calls to detect 1 valid call would be incredibly sloppy.

Instead, just pass the single object you clicked to a method which makes decisions about that single object. Event systems are useful when all other alternatives are somehow grossly inconvenient, but they are not a “magic bullet” programming technique.