Re: Query: want a function that is called at initialisation time

From:
Bart van Ingen Schenau <bart@ingen.ddns.info>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 16 Dec 2007 08:16:42 CST
Message-ID:
<1388352.Euuksrcuhl@ingen.ddns.info> <f4ec18d6-99c6-4f12-9473-06bfae69441c@t1g2000pra.googlegroups.com> <so6dnX8PeOeaGv3anZ2dnUVZ_qmlnZ2d@comcast.com> <b40da43f-3fbf-4e82-ae4f-3f6b55b74c40@d21g2000prf.googlegroups.com> <3333146.kfcRz2vtIt@ingen.ddns.info> <552f8ef7-3066-4319-8d1c-603b27683f03@i12g2000prf.googlegroups.com>
tropostropos@hotmail.com wrote:

Then I still have a problem. I am designing this for a large shop
(30+ developers, some in India) who will be routinely adding new
Singletons to a large body of software. I am making the interface as
simple as possible. The developer just has to derive their new class
MyClass like this:
     class MyClass: public Singleton<MyClass> { friend class
Singleton<MyClass>; . . . };

Is there any way I can avoid having to tell them, "by the way, if your
singleton class is called MyClass, you have to add the following line
somewhere in your code:
   int dummy = Singleton<MyClass>::initialise(); "

Because, sure as eggs is eggs, some of them will forget to add the
line.


If you reread my example in the previous post, you will see that I never
explicitly referenced 'Singleton<double>::do_initialise()' anywhere in
the code.

So, you could just do as I did: Have 'dummy' be a static member of
Singleton<T>, together with 'initialise()'.
Then you can just add the definition (outside the class) to the file
like this:
   template <class T> int Singleton<T>::dummy = initialise();

As long as you make sure that dummy is referenced somewhere in code that
must always be used (like the Singleton<T> constructor, or the
get_instance() function), there are no additional requirements on your
coworkers.

Thanks,
Tropos


Bart v Ingen Schenau
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