C# lambda 调用 for 循环引用最后一个对象

Question

我研究了这个问题，并尝试按照之前几个问题中的说明修复代码 (such as this one)，但它仍然无法正常工作。虽然我必须说我检查的所有答案都是从 2009 年到 2010 年的，所以它们可能已经过时了。

这是罪魁祸首代码:

            foreach(Entity player in players)
            {
                if(player.actions.Count > 0)
                {
                    Entity temp = player;

                    player.isDoingAction = true;
                    Debug.Log(player.name + " started action");

                    player.actions.Dequeue().Execute(() => { temp.isDoingAction = false; Debug.Log(temp.name + " finished"); });
                }
            }

这将打印以下内容:

Player1 started action
Player2 started action
Player2 finished
Player2 finished

什么时候应该打印:

Player1 started action
Player2 started action
Player1 finished
Player2 finished

或类似的东西。

此代码在 Unity 协程函数中运行。

代码的大一点:

GameManager.cs

private IEnumerator RunTurn()
{
    ...
    ...
    ...

    for(int i = 0; i < phases; i++)
    {
        //Assign action to each player
        foreach(Entity player in players)
        {
            if(player.actions.Count > 0)
            {
                Entity temp = player;

                player.isDoingAction = true;
                Debug.Log(player.name + " started action");
                player.actions.Dequeue().Execute(() => { temp.isDoingAction = false; Debug.Log(temp.name + " finished"); });
            }
        }

        //Wait for each player to finish action
        foreach(Entity player in players)
        {
            while(player.isDoingAction == true)
            {
                Debug.Log("Waiting for " + player.name);
                yield return null;
            }
        }
    }

    ...
    ...
    ...
}

Action.cs

public override void Execute(System.Action callback)
{
    Move(callback);             
}

private void Move(System.Action callback)
{
    ...
    ...
    ...

    //Move target entity
    target.MoveToPosition(newPosition, mSpeed, callback);
    target.location = newLocation;

    ...
    ...
    ...
}

Entity.cs

public void MoveToPosition(Vector3 position, float speed, System.Action callback)
{
    StartCoroutine(CoMoveToPosition(position, speed, callback));
}

//Move to position
private IEnumerator CoMoveToPosition(Vector3 position, float speed, System.Action callback)
{
    while(position != transform.position)
    {
        transform.position = Vector3.MoveTowards(transform.position, position, speed * Time.deltaTime);
        yield return null;
    }

    //Move finished so use callback
    callback();
}

解决方案

事实证明，Unity 中存在协程和匿名 lambda 回调的错误。检查this更多链接。

工作代码:

foreach(Entity player in players)
{
    if(player.actions.Count > 0)
    {
        player.isDoingAction = true;
        Debug.Log(player.name + " started action");

        System.Func<Entity, System.Action> action = new System.Func<Entity,System.Action>(p =>
        new System.Action(() => { p.isDoingAction = false; Debug.Log(p.name + " finished"); }));

        player.actions.Dequeue().Execute(action(player));
    }
}

Answer 1

您可以通过以下方式捕获值:

var action = new Func<Entity, Action>(p => 
new Action(() => { p.isDoingAction = false; Debug.Log(p.name + " finished")); })(player);
player.actions.Dequeue().Execute(action);