Using multiple files

Newbie alert: I'm learning about how to use multiple files to better organize code. Our book says that the class definitions go in a .h file while the class functions themselves go in an implementation file (.cpp or .cxx). Easy enough.

I have created a class called "circle". Following the above structure, I created two files called circle.h and circle.cpp. In the circle.cpp file, I have a line "#include circle.h".

Where does int main() go? I put it in a third file called "main.cpp". In that file, I added "#include circle.cpp (I also tried #include circle.h). In int main(), I have a line that creates a new circle (circle my_circle()), but it won't compile. I get an error message that says: "

from main.cpp
expected unqualified-id before '}' token
In function int main()':
circle was not declared in this scope
expected ';' before "my_circle"

Can somebody set me straight about how to integrate these various files? Thanks.

dams (41)

expected unqualified-id before '}' token

You may have forgotton a '}' in a declaration, definition or loop.

circle was not declared in this scope

Add header files using #include not .cpp files (add circle.h in main.cpp)

expected ';' before "my_circle"

Could be because you didn't add circle.h in main.cpp

LB (13399)

^{Edit: damn, dams beat me X)}
You don't include .cpp files. Ever. You only include header files. Your project should look similar to this:

Circle.h

//Include Guard
#ifndef _CircleClass_Header_
#define _CircleClass_Header_

class Circle
{
  unsigned long radius;
public:
  Circle(); //Default Constructor
  Circle(const unsigned long&); //Construct from a Radius
  Circle(const Circle&); //Copy Contructor
  Circle& operator=(const Circle&); //Operator =

  void SetRadius(const unsigned long&);
  unsigned long GetRadius();

  ~Circle(); //Destructor
}; //Note the semi-colon

#endif

Circle.cpp

#include "Circle.h"

Circle::Circle() : radius(0) //initialize radius to 0
{
}
Circle::Circle(const unsigned long& radius) : radius(radius) //initialize radius to the given parameter
{
}
Circle(const Circle& from) : radius(from.radius) //copy the radius from the other circle
{
}
Circle& Circle::operator=(const Circle& from)
{
  radius = from.radius;
}

void Circle::SetRadius(const unsigned long& newRadius)
{
  radius = newRadius;
}
unsigned long Circle::GetRadius()
{
  return(radius);
}

Circle::~Circle() //If you used pointers with new or new[] in the constructors, use delete or delete[] here
{
}

Main.cpp

#include <iostream>
using namespace std;
#include "Circle.h" //The other .cpp file provides the definitions, the linker will link it all together

int main()
{
  Circle a (5); //makes a circle with radius 5
  cout << a.GetRadius() << endl;
  Circle b (a); //b copies the radius from a
  cout << b.GetRadius() << endl;
  Circle c = a; //in this case it calls the copy constructor and not operator=
  cout << c.GetRadius() << endl;
  b.SetRadius(7); //changes b's radius to 7;
  cout << b.GetRadius() << endl;
  c = b; //this calls operator=
  cout << c.GetRadius() << endl;

  //Hold the window open until you press enter
  cin.sync();
  cin.ignore();
}

Last edited on

joatmon (157)

Got it. Thanks!

Topic archived. No new replies allowed.

C++

Forum

Using multiple files