Re: Differentiating pimpl idiom classes in c++

On 18 Apr, 02:35, Carl Barron <cbarron...@[EMAIL PROTECTED]
> wrote:
> > We are working with an embedded device where only one implementation
> > of the driver needs to be in memory at any moment in time.  The
> > implementation may vary due to variations in the hardware (this must
> > be a common issue).  The pimpl idiom seemed to fit the bill.

>   Pimple is to hide implementation details so they can be modifed
> without recompiling client code.   Here you want a to select one of
> k implementaions of a classes Driver and change them some how.

Indeed. Pimpl is all about reducing physical dependencies
by making it so that the class header file does not contain
any implementation details. Changing such details if they were
in the header would mean the header would change, which causes
any dependency-mgd build to recompile many files. This is a problem
for large projects.

>
> None of the classical OOP Patterns are done at link time, they are done
> at runtime.  If you use templates those used must be visiable at
> compile time,  and they solve a similiar problem at compile time.

The design pattern is 'strategy'. In the early days this was
done using virtual functions but people seem to prefer a
template based strategy these days. It does eliminate the
overhead of a virtual dispatch and this seems to be the quoted
reason for the preference.

Regards,

Andrew Marlow

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