包含类的传染媒介类

Question

我定义了两个类：

class Group
{
  public:
    Group ( void );
    bool addStudent ( const Student & X );
    void printAll( void ) const;

  protected:
    vector<Student> vectorOfStudents;
};
//-----------------------------------------------
class Student
{
   public:
     Student ( string name, int age );
     void printAtributes ( void );

   protected:
     string                    nameOfStudent;
     int                       ageOfStudent;
};

我正在创建对象并将它们存储在 Group 对象中以矢量但我想打印它们时遇到问题：

void Group::printAll ( void ) const
{
  for ( const auto &  student : vectorOfStudents )
  {
    student . printAtributes (  ); // Line 54
    cout << endl;
  }
}

这是每次调用并打印学生姓名的函数：

void Student::printAtributes ( void )
{
  cout << "name: " << nameOfStudent << " | " << "age: " << ageOfStudent<< endl;
}

给我这个错误：

54:33: error: passing ‘const Student’ as ‘this’ argument of ‘void Student::printAtributes()’ discards qualifiers [-fpermissive]
     student . printAtributes (  );

Answer 1

改变一下

void printAtributes ( void );

到

void printAtributes ( void ) const;
                          // ^^^^^

正如您从 const 引用中明确要求的那样

for ( const auto &  student : vectorOfStudents )
   // ^^^^^^^^^^^^

该函数必须声明为可从 const 引用中调用。