c# - 摆脱不必要的循环

Question

在我的游戏中，我将进行很多交互，在这些交互中我需要查看玩家是否拥有元素，如果他拥有并且其他情况为真，则执行操作。在下面的代码中描述。

private void SetTinderInPit()
{
    MouseState currentMouseState = Mouse.GetState();

    if (player.NextToFirePit == true)
    {
        foreach (Item item in player.PlayerInventory.Items)
        {
            if (item.ItemName == "tinder")
            {
                foreach (Item pit in allItemsOnGround)
                {
                    if (pit.ItemName == "firepit" && 
                        pit.ItemRectangle.Contains(MouseWorldPosition) &&
                        currentMouseState.LeftButton == ButtonState.Pressed &&
                        oldMouseState.LeftButton == ButtonState.Released)
                    {
                        item.ItemName = "empty";
                        pit.ItemName = "firepitwithtinder";
                        pit.Texture = Content.Load<Texture2D>("firepitwithtinder");
                    }
                }
            }
        }
        oldMouseState = currentMouseState;
    }
}

如您所见，这看起来很难看，我认为会有更好的方法来做到这一点，但我不确定如何做。由于会有很多此类方法，我想知道实现此目的的最佳方法是什么？

Answer 1

似乎您可以通过使用一些 LINQ 完全摆脱(实际上隐藏)循环:

private void SetTinderInPit()
{
    MouseState currentMouseState = Mouse.GetState();

    if (player.NextToFirePit)
    {
        Item tinder = player.PlayerInventory.Items.FirstOrDefault(i => i.ItemName == "tinder");
        if (tinder != null)
        {
            Item firepit = allItemsOnGround.FirstOrDefault(i => i.ItemName == "firepit" && i.ItemRectangle.Contains(MouseWorldPosition));
            if (firepit != null && 
                currentMouseState.LeftButton == ButtonState.Pressed &&
                oldMouseState.LeftButton == ButtonState.Released)
            {
                tinder.ItemName = "empty";
                firepit.ItemName = "firepitwithtinder";
                firepit.Texture = Content.Load<Texture2D>("firepitwithtinder");
            }
       }
       oldMouseState = currentMouseState;
    }
}

这具有在找到项目时使循环短路的额外优势。它还可以轻松检查名称以外的内容(例如“IsFlammable”或“CanContainFire”属性)，因此您可以使用多个项目而不仅仅是“tinder”和“firepit”。

如果您实际上打算移除所有火坑和火种，请使用:

private void SetTinderInPit()
{
    MouseState currentMouseState = Mouse.GetState();

    if (player.NextToFirePit)
    {
        foreach (Item tinder in player.PlayerInventory.Items.Where(i => i.ItemName == "tinder")
        {
            foreach (Item firepit in allItemsOnGround.Where(i => i.ItemName == "firepit"))
            {
               if (firepit.ItemRectangle.Contains(MouseWorldPosition) &&
                currentMouseState.LeftButton == ButtonState.Pressed &&
                oldMouseState.LeftButton == ButtonState.Released)
                {
                   tinder.ItemName = "empty";
                   firepit.ItemName = "firepitwithtinder";
                   firepit.Texture = Content.Load<Texture2D>("firepitwithtinder");
                }
             }
       }
       oldMouseState = currentMouseState;
    }
}

快速警告；此代码将移除带有第一个火种的所有火坑，而其他火种则毫发无损。我可以解开循环以删除所有内容，但此函数与提供的函数匹配；此外，我假设这不是预期的行为。

请注意，您在任何地方都不需要 ToList，因为您没有在枚举期间修改集合。您始终可以修改集合中的项目，以下测试证明了这一点:

class IntWrapper
{
    public int value;

    public IntWrapper(int value)
    {
        this.value = value;
    }
}

class Program
{
    static void Main(string[] args)
    {
        List<IntWrapper> test = new List<IntWrapper>() { new IntWrapper(1), new IntWrapper(2), new IntWrapper(3), new IntWrapper(4), new IntWrapper(5) };

        foreach (IntWrapper i in test.Where(i => i.value == 1))
        {
            i.value = 0;
        }

        foreach (IntWrapper i in test)
        {
            Console.WriteLine(i.value);
        }

        Console.ReadLine();
    }
}