Another approach is suggested by Herb Sutter in "Exceptional C++". See "the
pimpl idiom".
This is a summary:
It is good to minimize h file dependencies, and it is good to hide private
data from other classes. However, C++ doesn't have a good internal mechanism
to do this. The following style approximates it:
---- A.h ----
class AImpl; // forward declaration
class A
{
public:
... // all public access functions
private:
AImpl* m_pImpl;
};
---- A.cpp ----
#include "B.h"
class AImpl
{
public:
B m_B;
};
A::A()
: m_pImpl(new AImpl)
{}
A::~A()
{
delete m_pImpl;
}
void A::Function()
{
m_pImpl->m_B; // use B somehow.
}
It seems like a bit of extra work, and an extra memory allocation, but after
using it some, I just love the streamlined H files. It makes developing
client code much clearer.
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Ehsan Akhgari
> Sent: Tuesday, January 25, 2005 11:40 PM
> To: [email protected]
> Subject: RE: [msvc] header file inclusion
>
>
> > class A
> > {
> > .....
> > private:
> > class B;
> > };
> >
> > Assume A is defined in A.h and B is defined in B.h Here the
> > composition of A depends on the type B.
> >
> > Say code in file "one.cpp" wants to create objects of type A.
> > 1) Either in one.cpp we first include B.h followed by A.h OR
> > 2) We include B.h in the file A.h.
> >
> > Which approach is better ? I feel per module there must be a common
> > header file. Also, is it absolutely evil/bad to include header files
> > within header files?
>
> Actually, I would #include "B.h" in A.h, so that anywhere you
> include A.h,
> it just works without you needing to worry about what headers
> should be
> included before it.
>
> You should just use #include guards, or #pragma once to make
> sure the same
> header is not included multiple times in a translation unit.
>
> -------------
> Ehsan Akhgari
>
> Farda Technology (http://www.farda-tech.com/)
>
> List Owner: [email protected]
>
> [ Email: [EMAIL PROTECTED] ]
> [ WWW: http://www.beginthread.com/Ehsan ]
>
> Under conditions of peace the warlike man attacks himself.
> -Beyond Good And Evil, F. W. Nietzsche
>
>
>
>
> _______________________________________________
> msvc mailing list
> [email protected]
> See
> http://beginthread.com/mailman/listinfo/msvc_beginthread.com
> for subscription changes, and list archive.
>
_______________________________________________
msvc mailing list
[email protected]
See http://beginthread.com/mailman/listinfo/msvc_beginthread.com for
subscription changes, and list archive.
