3个.h和3个.cpp文件

Question

I'm building an application that should use one class from 1.h in 2.h it is defined like:

<classname> *p;

now i can use p in 2.cpp. But I would also like to use it in 3.cpp. I could not include the 2.h in 3.cpp. Is there a way to make it visible in 3.cpp?

Thanks for the help.

Answer 1

A more descriptive example of your problem with some code would be valuable.

In general attempt to do the following:

• Each header should contain only the its own class with the same name.
• If a class is using another class, and you can forwardly declare it in that header, do.

You cannot forwardly declare if the class has an instance of another class or if it derives from it.

• Compilation units (cpp) files should include all the headers they need. Ideally include its own header first.

Answer 2

You need to provide more info but I think I got it Your trying to use a class in a header that was defined I. A another header, but for some reason you can't include the header it was defined into the header your working on. The solution is to create a "temporary" definition instead of an include.

Eg: U need myClassA in 1.h but it was defined in 2.h and some error doesn't let you include 2.h into 1.h to solve it you.simply Write:

class myClassA;

on top of 1.h so you can reference it, but no implementation (because it is implemented in 2.cpp)

Answer 3

A simple rule is one class, one header file.

Given:

A.h:
class A
{
};

B.h:
#include "A.h"
class B
{
  A obj;
};

C.h:
#include "A.h"
class C
{
  A obj;
};

I hope this answers the question. Otherwise, edit your question with more details and example of what you are trying to accomplish.