C++工程,枚举类输出运算符重载，elaborated

C++工程,枚举类输出运算符重载，elaborated

文章目录

• 1,原始代码
• 2,运行没问题，但编译会有警告：elaborated-type-specifier for a scoped enum must not use the ‘class’ keyword
• 3,修改

1,原始代码

#include <iostream>enum class TreeType : int {PINE = 1,CYPRESS = 2,WILLOW = 3
};
std::ostream &operator<<(std::ostream &os, const enum class TreeType &rhs) {switch(rhs) {case TreeType::PINE:os << "PINE"; break;case TreeType::CYPRESS:os << "CYPRESS"; break;case TreeType::WILLOW:os << "WILLOW"; break;}return os;
};int main() {TreeType tree_type;tree_type = TreeType::WILLOW;std::cout << tree_type << std::endl;return 0;
}

2,运行没问题，但编译会有警告：elaborated-type-specifier for a scoped enum must not use the ‘class’ keyword

3,修改

#include <iostream>enum class TreeType : int {PINE = 1,CYPRESS = 2,WILLOW = 3
};
//std::ostream &operator<<(std::ostream &os, const enum class TreeType &rhs) {
// 改为
std::ostream &operator<<(std::ostream &os, const enum TreeType &rhs) {switch(rhs) {case TreeType::PINE:os << "PINE"; break;case TreeType::CYPRESS:os << "CYPRESS"; break;case TreeType::WILLOW:os << "WILLOW"; break;}return os;
};int main() {TreeType tree_type;tree_type = TreeType::WILLOW;std::cout << tree_type << std::endl;return 0;
}