在C ++中迭代通过连续枚举值的最简单的方法 [英] Simplest method for iterating through contiguous enum values in C++

问题描述

在C ++中使用连续值迭代枚举的首选简单方法是什么？我发现以前的SO这个问题涉及创建自定义操作符++ 等，但这似乎过度。到目前为止，我想出的最好的是：

What is the preferred simple method for iterating through an enum with contiguous values in C++? I found previous SO questions on this subject which involved creating custom operator++ etc, but this seems like overkill. So far the best I have come up with is:

enum {
   FOO,
   BAR,
   BLECH,
   NUM_ENUMS
} MyEnum;

//for (MyEnum m = FOO; m < NUM_ENUMS; ++m)             // compile error
//    ...

//for (MyEnum m = FOO; m < NUM_ENUMS; m = m + 1)       // compile error
//    ...

for (MyEnum m = FOO; m < NUM_ENUMS; m = MyEnum(m + 1)) // OK ?
    ...

从编码风格的角度来看，这是合理的，警告（ g ++ -Wall ... 似乎对此感到满意）？

Is this reasonable from a coding style perspective and is it likely to generate warnings (g++ -Wall ... seems happy with this) ?

推荐答案

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这将是未定义的： MyEnum（int（NUM_ENUMS）+ 1）因为保持（4）的值将大于枚举可以表示的值（[0,3]）;由于您确保 m 严格低于 NUM_ENUMS ，可以安全地使用 MyEnum + 1）。

This would have been undefined: MyEnum(int(NUM_ENUMS) + 1) because the value to hold (4) would be greater than what the enum can represent ([0, 3]); since you ensure that m is strictly lower than NUM_ENUMS it is safe to use MyEnum(m + 1).

另一方面，请注意，您会遇到自定义枚举的问题，例如：

On the other hand, note that you would have issues with customized enums such as:

enum OtherEnum {
    Foo = -1,
    Bar = 2,
    Baz = 8,
    NUM_OTHERENUM
};

因此不是通用做法。

我建议生成的数组迭代，代替：

I would advise a generated array to iterate over instead:

MyEnum const Values[] = { FOO, BAR, BLECH };

请注意，它很容易从枚举的定义生成，无意义的价值（商业智慧）。

Note that it is easily generated from the definition of the enum, and also avoid polluting the interface with a nonsensical value (business-wise).

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