展开的循环工作，用于循环无效

Question

我有一些我不理解的行为。虽然展开的循环效果很好！！！循环抛出indexoutofrangeExceptions。调试表明那里有0..9 Teambuttons和0..9卡C [I]。：（

private void Awake()
{
    InitCards();
    // This works!
    teamButtons[0].onClick.AddListener(() => SetCard(c[0]));
    teamButtons[1].onClick.AddListener(() => SetCard(c[1]));
    teamButtons[2].onClick.AddListener(() => SetCard(c[2]));
    teamButtons[3].onClick.AddListener(() => SetCard(c[3]));
    teamButtons[4].onClick.AddListener(() => SetCard(c[4]));
    teamButtons[5].onClick.AddListener(() => SetCard(c[5]));
    teamButtons[6].onClick.AddListener(() => SetCard(c[6]));
    teamButtons[7].onClick.AddListener(() => SetCard(c[7]));
    teamButtons[8].onClick.AddListener(() => SetCard(c[8]));
    // This yields an IndexOutOfRangeException
    for (int i = 0; i < 9; ++i)
    {
      teamButtons[i].onClick.AddListener(() => { SetCard(c[i]); });
    } 
}

Answer 1

您正在捕获lambda表达式中的 i。当执行该lambda表达式时，它将使用i的"当前"值 - 它将始终为9。您想捕获变量的 copy ...循环中的新变量：

for (int i = 0; i < teamButtons.Length; i++)
{
    int index = i;
    teamButtons[i].onClick.AddListener(() => SetCard(c[index]));
}