enum类不是类或名称空间。

I have a problem with the enum class feature of c++11. A minimal code example is:

我对c++11的enum类特性有一个问题。一个最小的代码示例是:

template<typename T>
class AClass{
public: 
enum class paramNames{
    PA = 0,
    PB,
    PC,
    NUM
};

private:
double params[paramNames::NUM];
}

when I want to compile a program, which uses this program with gcc I get the following error message:

当我想要编译一个程序，它使用这个程序与gcc时，我得到以下错误信息:

error: 'paramNames' is not a class or namespace double params[paramNames::NUM];

错误:“paramNames”不是类或名称空间双参数[paramNames: NUM];

I would appreciate, if someone can explain to me, how to use the new enum class feature correctly.

如果有人能向我解释如何正确地使用enum类特性，我将不胜感激。

1 个解决方案

#1

Unlike the old enum there is no implicit conversion to int. By design enum class cannot be converted to the underlying type implicitly. You can read more about the justification for that here: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2347.pdf. To do what you want you need to use a static cast and do something like this:

与旧的enum不同，它没有对int的隐式转换。通过设计enum类不能隐式地转换为底层类型。您可以在这里阅读更多的理由:http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2347.pdf。要做你想做的事，你需要使用静态石膏，并做如下的事情:

template<typename T>
class AClass{
public: 
enum class paramNames: int{//specify the underlying type
    PA = 0,
    PB,
    PC,
    NUM
};

private:
    double params[static_cast<int>(paramNames::NUM)];
}

EDIT: Make sure your compiler has the c++11 language features available to it, otherwise you will get errors doing this.

编辑:确保你的编译器有c++11语言的特性，否则你会在这方面出错。