Re: Should you perform complex tasks in the constructor?

From:
Chicken McNuggets <chicken@mcnuggets.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 11 Jan 2013 12:42:18 +0000
Message-ID:
<kcp1b8$p5o$2@speranza.aioe.org>
On 10/01/13 22:21, Greg Martin wrote:

On 13-01-10 01:54 PM, Chicken McNuggets wrote:

I've seen various arguments against this primarily centring on the fact
that the only way to return errors in a constructor is to throw an
exception. Of course exceptions seem to be a somewhat controversial
subject in the C++ community so I'll try and avoid touching on that.

But I have a couple of classes that are created when the program
launches and are freed just before the program terminates. It makes
sense for me to put a lot of logic in the constructor as these classes
are initialised from data in different configuration files which are
passed as command line arguments.

Is there any reason I shouldn't put all the file loading / reading /
storing of data in the constructor? Or would you not consider this a
problem? For reference I'm using libxml2 for reading the data in the
configuration files.


In cases where it makes sense I set error variables to be tested, just
like a returned value, after the constructor completes.

e.g.
File *f = new File (path);
if (!f->success ()) {
     std::cerr << f->error () << std::endl;
     // cleanup
}


Yeah I considered this approach but it has a tendency to expose the
inner workings of the class if you are not careful, and I'd like to make
sure that re-writing the class in the future to take into account more
configuration options does not lead to a re-write of critical pieces of
the code since this class is of crucial importance to the rest of the
program.

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