C++核心准则Enum.2: 使用枚举表现一组相关的命名常量

Enum.2: Use enumerations to represent sets of related named constants

Enum.2: 使用枚举表现一组相关的命名常量

Reason(原因)

An enumeration shows the enumerators to be related and can be a named type.

枚举类型表示枚举值之间具有相关性，并且可以成为命名类型。

Example(示例)

enum class Web_color { red = 0xFF0000, green = 0x00FF00, blue = 0x0000FF };

Note(注意)

Switching on an enumeration is common and the compiler can warn against unusual patterns of case labels. For example:

启用枚举类型属于常规操作，并且编译器可以对不平常的用法进行警示。例如：

enum class Product_info { red = 0, purple = 1, blue = 2 };

void print(Product_info inf)
{
    switch (inf) {
    case Product_info::red: cout << "red"; break;
    case Product_info::purple: cout << "purple"; break;
    }
}

Such off-by-one switch-statements are often the results of an added enumerator and insufficient testing.

这种"只越界一点"的switch语句通常是增加枚举值后没有充分测试的结果。

Enforcement(实施建议)

• Flag switch-statements where the cases cover most but not all enumerators of an enumeration.
• 提示switch语句覆盖大多数枚举值却没有覆盖所有枚举值的情况。
• Flag switch-statements where the cases cover a few enumerators of an enumeration, but has no default.
• 提示swtich语句覆盖了少数枚举值却没有default分支的情况。

原文链接：

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#enum2-use-enumerations-to-represent-sets-of-related-named-constants

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