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c#unity-game-enginesubscribe
Shady Gheith
Shady Gheith

Reputation: 7

How to use string delegate subscribed to 2 methods

I have 2 C# classes one of them has a string delegate and the other subscribes an function to that delegate.

My question is I want to combine the two called string functions from the delegate instead of choosing the return value between them randomly

delgatesystem.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class delegatesystem : MonoBehaviour {

public delegate string MyDelegate();
public static event MyDelegate MyEvent;
string GameObjectsNames = "";

void Update ()
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        if (MyEvent != null)
         {
           GameObjectsNames +=  MyEvent();
         }
       }
    }
}

delegatesave.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class delegatesave : MonoBehaviour {

void Start ()
{
    delegatesystem.MyEvent += DelegateFunction;
}

string DelegateFunction()
{
    return gameObject.name;
}
}

note: the delgatesave.cs is attached to 2 gameobjects.

Upvotes: 0

Views: 307

Answers (1)

György Kőszeg
György Kőszeg

Reputation: 18033

First of all, creating events with non-void delegates is an antipattern. Events are typically used with potentially more subscribers.

If a non-void multicast delegate is invoked with multiple subscribers, always the return value of the last subscribed method is returned.

But after all you can do something like this:

string[] objectNames = MyEvent.GetInvocationList().Cast<MyDelegate>().Select(del => del()).ToArray();

However, a better solution would be to use more conventional events:

public class PopulateNamesEventArgs : EventArgs
{
    private List<string> names = new List<string>();
    public string[] Names => names.ToArray();
    public void AddName(string name) => names.Add(name);
}

And then in your class:

public event EventHandler<PopulateNamesEventArgs> MyEvent;

protected virtual void OnMyEvent(PopulateNamesEventArgs e) => MyEvent?.Invoke(this, e);

Invokation:

var e = new PopulateNamesEventArgs();
OnMyEvent(e);
string[] objectNames = e.Names; // the result is now populated by the subscribers

Subscription:

void Start()
{
    delegatesystem.MyEvent += DelegateFunction;
}

void DelegateFunction(object sender, PopulateNamesEventArgs e)
{
    e.AddName(gameObject.name);
}

Upvotes: 2

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