C++11的强类型枚举

C++之前的枚举的成员名字是全局可见的，下面的情况就会报错

enum Book1{red = 1, blue = 2, green = 3, black = 4};
enum Book2{red = 1, yellow = 2};

Book1和Book2都含有red，就会出现冲突，C++11枚举解决了这个问题：

enum class Book1{red = 1, blue = 2, green = 3, black = 4};
enum class Book2{red = 1, yellow = 2};

int main() {
	Book1 test = static_cast<Book1>(2);
	switch (test) {
		case Book1::red:
			std::cout << "red" << std::endl;
			break;
		case Book1::blue:
			std::cout << "blue" << std::endl;
			break;
		case Book1::green:
			std::cout << "green" << std::endl;
			break;
		case Book1::black:
			std::cout << "black" << std::endl;
			break;
	}
	return 0;
}

强类型枚举不能和int类型直接转换，必须进行强转！