Classes in separate files in C++? - c++

Question

I have copied this out of a book. I'm just not sure what to add in the main.cpp source file to make it run though.
I know that class declarations go in the .h file and implementations go in the .cpp file. What would I need to write in main.cpp?
I've tried lots of different things but I'm just getting so many error messages.
// cat.h
#ifndef ____2_cat_implementation__Cat__
#define ____2_cat_implementation__Cat__
#include <iostream>
using namespace std;
class Cat
{
public:
Cat (int initialAge);
~Cat();
int GetAge() { return itsAge;}
void SetAge (int age) { itsAge = age;}
void Meow() { cout << "Meow.\n";}
private: int itsAge;
};
#endif /* defined(____2_cat_implementation__Cat__) */
...
// cat.cpp
#include <iostream>
#include "Cat.h"
using namespace std;
Cat::Cat(int initialAge)
{
itsAge = initialAge;
}
Cat::~Cat()
{
}
int main()
{
Cat Frisky(5);
Frisky.Meow();
cout << "Frisky is a cat who is ";
cout << Frisky.GetAge() << " years old.\n";
Frisky.Meow();
Frisky.SetAge(7);
cout << "Now Frisky is " ;
cout << Frisky.GetAge() << " years old.\n";
return 0;
}

Answer 1

Look at this part again:
Cat::Cat(int initialAge);
{
itsAge = initialAge;
Cat::~Cat()
You're missing the closing } for the constructor, as well as an extra ; after the function header.
On an unrelated note, don't use global names starting with underscore (like ____2_cat_implementation__Cat__), those names a reserved by the specification.

Answer 2

You have a missing } and unneccessary ;
//----------------------v
Cat::Cat(int initialAge);
{
itsAge = initialAge;
}
//^
What would I need to write in main.cpp
Usially, as you have pointed out, the .h file contains the declarations and the .cpp file - the definitions. Then, the main.cpp file should contain the main function (it's not necessary to name the file, containing the main function main.cpp. It could be anything.
So, in your example, you can create a main.cpp file with the following content:
// include the declarations file
#include "cat.h"
// include the header for cin/cout/etc
#include <iostream>
using namespace std;
int main()
{
Cat Frisky(5);
Frisky.Meow();
cout << "Frisky is a cat who is ";
cout << Frisky.GetAge() << " years old.\n";
Frisky.Meow();
Frisky.SetAge(7);
cout << "Now Frisky is " ;
cout << Frisky.GetAge() << " years old.\n";
return 0;
}
Other notes:
using namespace std; is bad practice, especially in header files. Use std:: instead (for example, std::cout, std::cin, std::string, etc)
as you have .h and .cpp files, don't put half of the implementation in the header and the rest - in the source file. Put all definitions inside the source files (unless you want to inline the functions, implemented in the header)
avoid using names, starting with __ or _ - they are reserved by the standard.