C ++如何访问内部枚举类？ [英] C++ How can I access to an inner enum class?

问题描述

我在c ++中遇到问题：

I am facing a problem in c++:

#include <iostream>
 class Apple{
public:
    int price = 100;
    enum class color {
    red =1, green, yellow
    };



};
int main() {
 Apple apple;
 std::cout << Apple::color::green << std::endl;

}

当我尝试编译此代码时，出现以下消息：

When I try to compile this code following message appears:

[错误]'Apple :: color'不是类或命名空间

[Error] 'Apple::color' is not a class or namespace

推荐答案

P0W的答案在两个方面都是正确的，但是如果您只想输出基础值，则强制转换而不是重载可能更简单。

P0W's answer is correct on both counts, but in case you simply want to output the underlying value, then it may be simpler to cast rather than overload the insertion operator.

using enum_type = std::underlying_type<Apple::color>::type;
enum_type value = (enum_type)Apple::color::green;
std::cout << value << '\n';

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