如何在 Unity/C# 中传递要添加到事件的函数？

Question

I am trying to create some inheritance class structures. After learning about events, I wanted to use them in some way. My intent is to have an abstract class that requires child classes to implement an OnDeath UnityEvent. I have tried using System.Func and Delegates, but neither have worked for me. I have included what I have tried, and the errors I received from trying those. Is there a way to have an abstracted function that lets me add a function to the event invoker? Am I just overcomplicating the process?

To clarify: I am aware of the differing types, and why the types are resulting in this error. My question comes lies in what type I should be going with here. I have no idea what a Unity Action is, or how to even define such an object if I wanted to use it.

Using Delegates

EntityManager.cs with delegate

using UnityEngine;
using UnityEngine.Events;
using System;

public abstract class EntityManager : MonoBehaviour
{
    public EntityManager()
    {
        if (OnDeathEvent == null)
        {
            OnDeathEvent = new UnityEvent();
        }
        OnDeathEvent.AddListener(OnDeath);
    }
    public abstract bool IsAlive();
    public delegate void Function();
    public abstract void AddOnDeathListener(Function f);
    public abstract void OnDeath();
    public UnityEvent OnDeathEvent;
}

EnemyManager.cs with delegate

using System;

public class EnemyManager : EntityManager
{
    private Enemy _enemy;
    public Enemy Enemy { get => _enemy; set => _enemy = value; }

    private void Awake()
    {
        _enemy = new Enemy();

    }

    public override bool IsAlive()
    {
        return Enemy.IsAlive();
    }

    public void NextEnemy()
    {
        Enemy = new Enemy();
    }

    public override void OnDeath()
    {
        NextEnemy();
    }

    public override void AddOnDeathListener(Function f)
    {
        OnDeathEvent.AddListener(f);
        // cannot convert from 'EntityManager.Function' to 'UnityEngine.Events.UnityAction'
    }
}

Using Func

EntityManager.cs with Func

    public abstract void AddOnDeathListener(Func<object> f);

EnemyManager.cs with Func

    public override void AddOnDeathListener(Func<object> f)
    {
        OnDeathEvent.AddListener(f);
        // cannot convert from 'System.Func<object>' to 'UnityEngine.Events.UnityAction'
    }

Edit: Normal functions in Unity seem to create UnityAction objects, rather than generic Func objects, which is an extremely essential distinction to be made. By reframing the question through this lens, the accepted answer makes a lot of sense.

Answer 1

You should change the AddOnDeathListener method to take a UnityAction instead of a Func or anything else, because the AddListener method of the UnityEvent class takes a UnityAction delegate as an argument.

Your code in the abstract class should look like this:

 public abstract void AddOnDeathListener(UnityAction f);

   

Answer 2

UnityEvents are not the same thing as C# Events in the System namespace, and UnityAction are not the same thing as C# Actions in the System namespace. But in your code you are mixing the two, with OnDeathEvent being in the UnityEngine.Events namespace and Func being in System . The reason you're having a compiler issue is that the UnityEvent.AddListener method takes a UnityAction argument, not a System.Func .

To fix, you will either need to switch your OnDeathEvent to being a C# event, or change your AddOnDeathListener to take UnityAction as an argument.

References:

https://docs.unity3d.com/ScriptReference/Events.UnityEvent.AddListener.html https://www.jacksondunstan.com/articles/3335

Code Sample:

public class CoolAbstract : TestMeAbstract
{
    UnityEvent SomeKindOfEvent;

    private void Start()
    {
        SomeKindOfEvent = new UnityEvent();

        AddOnDeathListener(() => { Debug.Log("Cool Abstraction"); });
    }

    private void Update()
    {
        if(Input.GetKeyDown(KeyCode.A))
        {
            SomeKindOfEvent.Invoke();
        }
    }

    public override void AddOnDeathListener(UnityAction ua)
    {
        SomeKindOfEvent.AddListener(ua);
    }
}

public abstract class TestMeAbstract : MonoBehaviour
{
    public abstract void AddOnDeathListener(UnityAction ua);
}