小编use*_*308的帖子

如果我创建一个类：

// First Example
#include <iostream>
#include <string>

class my_class {
  std::string str;
public:
  my_class(const char* s = "") : str(s) {}

  operator const char* () const { return str.data(); } // accessor
};

my_class mc1{"abc"};
std::cout << mc1; // Calls the char* accessor and successfully writes "abc" to screen output.

如果我这样修改类：

// Second Example
class my_class {
  std::string str;
public:
  my_class(const char* s = "") : str(s) {}

  operator std::string () const { return str; } // accessor
}; …