C#lambda调用for循环引用最后一个对象 [英] C# lambda call in for loop references to last object
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问题描述
我已经研究了这个问题,并且尝试按照之前几个问题中的说明修复代码(
I've researched this problem and I've tried fixing the code as instructed in a few questions before (such as this one) but it still won't work. Though I must say that all the answers I checked were from 2009-2010 so they might be obsolete.
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
何时打印:
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.
This code runs in a Unity coroutine function.
代码中的片段较大:
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中存在带有协程和匿名Lambda回调的错误.在此链接中进行检查更多.
It turns out there is a bug in Unity with coroutines and anonymous lambda callbacks. Check this link for more.
有效的代码段:
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));
}
}
推荐答案
您可以通过以下方式捕获值:
You can capture the value the following way:
var action = new Func<Entity, Action>(p =>
new Action(() => { p.isDoingAction = false; Debug.Log(p.name + " finished")); })(player);
player.actions.Dequeue().Execute(action);
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