Private/public header example?

Question

Can someone please give me an example of how public and private headers work? I have done some reading on the net but I can't seem to find much useful information with sample codes. I was advised that I should use private headers to separate the public and private parts of my code for creating a static library. After some reading I have a general idea of how it works, but would really appreciate a good example to get me started. Specifically, what I don't quite understand is how to put the interface functions in my public header, and the private variables/functions in my private header? Thanks!

EDIT:

Maybe I'm not wording my question right, but what I meant is, for example, I have myMath.h and myMath.cpp, and myMath.h has:

class myMath{ public:     void initialise(double _a, double _b);     double add();     double subtract();  private:     double a;     double b; }; 

And myMath.cpp has the implementations of the functions. How can I make it so that myMath.h only has the three public functions, and the private variables are defined in another file (e.g. myMath_i.h), and these three files are in such a way that after I create a static library, only myMath.h is needed by users. This also means myMath.h cannot #include myMath_i.h. So something like:

myMath.h:

class myMath{ public:     void initialise(double _a, double _b);     double add();     double subtract(); } 

and myMath_i.h:

class myMath{ private:     double a;     double b; } 

Of course that's not possible because then I'll be redefining the class myMath...

Answer 1

You have two header files MyClass.h and MyClass_p.h and one source file: MyClass.cpp.

Lets take a look at what's inside them:

MyClass_p.h:

// Header Guard Here class MyClassPrivate { public:     int a;     bool b;     //more data members; } 

MyClass.h:

// Header Guard Here class MyClassPrivate; class MyClass { public:     MyClass();     ~MyClass();     void method1();     int method2(); private:     MyClassPrivate* mData; } 

MyClass.cpp:

#include "MyClass.h" #include "MyClass_p.h"  MyClass::MyClass() {     mData = new MyClassPrivate(); }  MyClass::~MyClass() {     delete mData; }  void MyClass::method1() {     //do stuff }  int MyClass::method2() {     return stuff; } 

Keep your data in MyClassPrivate and distribute MyClass.h.