Question

我正在玩继承。我完全被编译器困惑了错误我得到并查找它似乎与我正在尝试的完全无关这样做只是初始化我的课程。

这里是错误：

    In file included from main.cpp:2:0:
student.h: In constructor ‘Student::Student(std::string, int, std::string, double)’:
student.h:13:3: error: class ‘Student’ does not have any field named ‘gnu_dev_major’
student.h: In function ‘std::ostream& operator<<(std::ostream&, const Student&)’:
student.h:25:8: error: no match for ‘operator<<’ in ‘os << "Name\011: "’
student.h:25:8: note: candidates are:
student.h:24:16: note: std::ostream& operator<<(std::ostream&, const Student&)
student.h:24:16: note:   no known conversion for argument 2 from ‘const char [8]’ to ‘const Student&’
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
student.h:25:32: error: ‘endl’ is not a member of ‘std’
student.h:26:8: error: no match for ‘operator<<’ in ‘os << "Age\011: "’
student.h:26:8: note: candidates are:
student.h:24:16: note: std::ostream& operator<<(std::ostream&, const Student&)
student.h:24:16: note:   no known conversion for argument 2 from ‘const char [7]’ to ‘const Student&’
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
student.h:26:30: error: ‘endl’ is not a member of ‘std’
student.h:27:8: error: no match for ‘operator<<’ in ‘os << "Major\011: "’
student.h:27:8: note: candidates are:
student.h:24:16: note: std::ostream& operator<<(std::ostream&, const Student&)
student.h:24:16: note:   no known conversion for argument 2 from ‘const char [9]’ to ‘const Student&’
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
student.h:27:34: error: ‘endl’ is not a member of ‘std’
student.h:28:8: error: no match for ‘operator<<’ in ‘os << "GPA\011: "’
student.h:28:8: note: candidates are:
student.h:24:16: note: std::ostream& operator<<(std::ostream&, const Student&)
student.h:24:16: note:   no known conversion for argument 2 from ‘const char [7]’ to ‘const Student&’
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
student.h:28:30: error: ‘endl’ is not a member of ‘std’
main.cpp: In function ‘int main()’:
main.cpp:8:2: error: ‘cout’ was not declared in this scope

令我困惑的是我得到的第一个错误：

student.h：在构造函数'Student :: Student（std :: string，int， std :: string，double）'：student.h：13：3：错误：类'学生'没有有任何名为'gnu_dev_major'的字段

这是我的代码：

  1 #ifndef STUDENT_H
  2 #define STUDENT_H
  3 
  4 #include <iostream>
  5 #include <string>
  6 #include "person.h"
  7 
  8 class Student : public Person {
  9         friend std::ostream & operator<<(std::ostream &,const Student &);
 10 public:
 11         Student(std::string name, int age, std::string m="undecided", double gpa=0.0) :
 12                 Person::Person(name,age),
 13                 major(m),
 14                 gpa(gpa)
 15         {}
 16 
 17 
 18 
 19 protected:
 20         double gpa;
 21         std::string major;
 22 };
 23 
 24 std::ostream & operator<<(std::ostream &os,const Student &s){
 25         os << "Name\t: " << s.name << std::endl;
 26         os << "Age\t: " << s.age << std::endl;
 27         os << "Major\t: " << s.major << std::endl;
 28         os << "GPA\t: " << s.gpa << std::endl;
 29 }
 30 
 31 #endif

如果有人指出我的重载可能出错的地方运算符＆lt;＆lt;对此的帮助也很感激=）。

Answer 1

你需要声明你的重载＆lt;＆lt;作为你班上朋友的操作员：

在您的Student类中声明如下：

class Student {
    // rest of code
    friend std::ostream & operator<<(std::ostream &os,const Student &s);
}

C ++错误构造函数参数

1 个答案: