C++ 错误构造函数参数

Question

我在玩继承。我对编译器完全感到困惑 我得到的错误并查找它似乎与我正在尝试的完全无关 要做的就是初始化我的类。

以下是错误：

    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

让我困惑的是我遇到的第一个错误：

student.h: 在构造函数'Student::Student(std::string, int, std::string, double)': student.h:13:3: error: class ‘Student’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

如果有人知道我的重载可能出了什么问题 操作员

Answer 1

你需要在你的类中声明你重载的

在 Student 类中声明如下：

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