While that allows you to use the string class, the relevant operator<< is defined in the <string> header itself, so you must include that manually
为什么有时候使用visual c++会提示 cout << 不能输出 string 类型: 因为 <iostream> 包含了头文件 <xstring>, 该头文件引入了 string 类型但是未引入 operator<<