Bdtjtk

I am learning c++ inheritance and here I have a problem.
if I make this simple code all in main.cpp file it will works without any
problem.

but when I seperate the files in header file and else
it won't work and it gives me some errors.

here is the code of header file named book.h

 #ifndef BOOK_H

 #define BOOK_H



 class book

{

 private:

 string name;



 public:

 book(string n = "default") : name(n) {};

 ~book() {};

 void printname();

};



#endif

and here is the code of book.cpp that I defined the function of this class
in this file.

#include <iostream>

#include <Windows.h>

#include <string>

#include "book.h"



using namespace std;



void book::printname()

{

 cout << name << endl;

 return;

}

and finally the main.cpp file:

#include <iostream>

#include <Windows.h> 

#include <string>

#include "book.h"



using namespace std;



 int main()

{

 system("color 0A");

 book programing("c++");

 cout << "the name of the book is ";

 programing.printname();



 system("pause");

 return;

}

and the errors that I get:

Severity Code Description Project File Line Suppression State

Error C2065 'name': undeclared identifier book d:vs
programbookbookbook.cpp 10

Error C3646 'name': unknown override specifier book d:vs
programbookbookbook.h 7

Error C4430 missing type specifier - int assumed. Note: C++ does not
support default-int book d:vs programbookbookbook.h 7

Error C2061 syntax error: identifier 'string' book d:vs
programbookbookbook.h 10

Error C2065 'n': undeclared identifier book d:vs
programbookbookbook.h 10

Error C2614 'book': illegal member initialization: 'name' is not a
base or member book d:vs programbookbookbook.h 10

Error C3646 'name': unknown override specifier book d:vs
programbookbookbook.h 7

Error C4430 missing type specifier - int assumed. Note: C++ does not
support default-int book d:vs programbookbookbook.h 7

Error C2061 syntax error: identifier 'string' book d:vs
programbookbookbook.h 10

Error C2065 'n': undeclared identifier book d:vs
programbookbookbook.h 10

Error C2614 'book': illegal member initialization: 'name' is not a
base or member book d:vs programbookbookbook.h 10

and other errors...

You need to make sure that string is a valid type in the .h file.

1. Add #include <string>.


2. Use std::string instead of just string.

#ifndef BOOK_H

#define BOOK_H



#include <string>



class book

{

   private:

      std::string name;



   public:

      book(std::string n = "default") : name(n) {};

      ~book() {};

      void printname();

};



#endif

This answer appears to address your question.
As a side note, since C++11, you can also specify default values for class members. So you could just do this instead:

#ifndef BOOK_H

#define BOOK_H



#include <string>



class book

{

   private:

      std::string name = "default";



   public:

      book() = default;

      book(std::string n) : name(n) {};

      ~book() {};

      void printname();

};



#endif