“用于C ++ / CLI中的每个”语句

array<int> ^ints = gcnew array<int>{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
for each(int i in ints)
    if(i % 2 == 0)
        Debug::WriteLine("Even\n");
    else
        Debug::WriteLine("Odd\n");

Why does the above fail to compile? It works fine if I use a for(int i; ...) or if I enclose the if-else within braces. I know that the manual clearly indicates that braces are required, but I want to know why this departure from expected behaviour?

为什么以上都无法编译?如果我使用for(int i; ...)或者将if-else括在大括号中,它可以正常工作。我知道手册清楚地表明需要括号,但我想知道为什么这会偏离预期的行为?

2 个解决方案

#1

I can't find any official documentation on it, but I can confirm the behavior you're seeing. It simply appears that the compiler is overly aggressive about finding the single statement following the for each, to the point of splitting the else from the if. It compiles it as if you had written the following, which is clearly incorrect.

我找不到任何关于它的官方文档,但我可以确认你看到的行为。只是看起来编译器过于积极地找到跟随for的每个单个语句,以及将if与if分开。它编写它就好像你写了以下内容,这显然是不正确的。

array<int> ^ints = gcnew array<int>{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
for each(int i in ints)
{
    if(i % 2 == 0)
        Debug::WriteLine("Even\n");
}
else
    Debug::WriteLine("Odd\n");

This is obviously different to how a regular C++ for loop behaves, so you may wish to file a bug at http://connect.microsoft.com.

这显然不同于常规C ++ for循环的行为,因此您可能希望在http://connect.microsoft.com上提交错误。

#2

I'm not a CLI export but I believe that for each (i in ints) is what you are after.

我不是CLI导出,但我相信每个(我在ints)就是你所追求的。

Edit

I checked the C++ source that I have available and we are using:

我检查了我可用的C ++源代码,我们正在使用:

for each (int i in ints) {
   // body
}

Is it possible that the braces are required? I don't have an MSFT compiler handy or I would try the following:

是否可能需要牙箍?我没有方便的MSFT编译器,或者我会尝试以下方法:

for each (int i in ints) {
    if(i % 2 == 0) {
        Debug::WriteLine("Even\n");
    } else {
        Debug::WriteLine("Odd\n");
    }
}