Re: Is there a preferred way of wrapping an object?
* DeMarcus, on 16.06.2010 15:57:
Please correct me if I'm wrong, but chaining is the only really good
solution to provide optional parameters when the number of parameters
grow large.
Jeff Flinn has alredy mentioned the Boost Parameters Library, which does not
depend on chaining.
But it is a bit impractical for constructor arguments in the context of inheritance.
Since the number of permutations of the optional parameters is so great
I cannot have them in the constructor of SomeObject. My first thought
was to create something like
SomeObjectA
SomeObjectB
...
SomeObjectQ
for each permutation, but I skipped that since I didn't want to force
the programmer to create an object for each permutation, hence the
general SomeObject with chaining.
Now, I still want to provide the /ability/ of creating SomeObjectA, etc.
(or functions) for the reason that it forces a compile-time check of the
provided parameters. Now the programmer can pinpoint certain often-used
permutations and make sure they will always get right. E.g.
startCalculation( DefaultSettings() );
All ideas about optional parameters are welcome. Thanks for your input!
Usage examples for a general chaining-based solution that supports inheritance
(i.e., it generates covariant setters) is available here:
http://alfps.wordpress.com/2010/05/19/cppx-how-to-do-typed-optional-arguments-in-c98/
It links further to the FAQ, to a DDJ article, to an earlier article posted in
this group, to earlier discussion in [comp.lang.c++], and to full code for the
discussed general solution in a ZIP archive at Google Docs.
The DDJ article additionally gives a usage example for the Boost Parameters
Library (possibly not the cleanest possible but the best that I could think of),
and discusses why BPAL may be undesirable and chaining preferable.
Cheers & hth.,
- Alf
--
blog at <url: http://alfps.wordpress.com>
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]