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Internet Message Format | 1996-08-06 | 2.2 KB

Path: news.th-darmstadt.de!news!enno
From: [e-mail] (Enno Sandner)
Newsgroups: comp.lang.c++
Subject: Re: Why use private class members instead of protected?
Date: 14 Jan 1996 16:30:34 GMT
Organization: Fachbereich Informatik, TH Darmstadt
Distribution: world
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In-reply-to: [e-mail]'s message of 14 Jan 1996 08:05:33 GMT

In article <[e-mail]> [e-mail] (Johan Wikman) writes:

   In article <[e-mail]> Enno Sandner <[e-mail]> writes:

      However an accessor/mutator pair like

              void MyClass :: set_data(const DataType&) { ... }
              DataType MyClass :: get_data() const { return _data; }

      completely avoids this sort of problems. If the 'DataType' uses some
      technique to speed up copying (for example ref-counting) the overhead
      is minimal.

   I think you only change the problem into something else. Now if you
   ever choose to change the representation of '_data' you face the
   problem of converting a DataType to and from whatever type '_data'
   is. The problem is still there, it has only changed shape.

Nevertheless it adds some sort of 'stability' to the class, because
necessary conversions can performed without changing the interface.
So, _if_ you need to access data-members of the base-classe(s) it's
_often_ a better choice to use accessor/mutator pairs compared to
making all data-members protected.

   In my opinion it fairly seldom makes sense to provide accessor/mutator
   functions to the data members of a class. In fact, I get suspicious
   when a class reminds you of a data repository instead of reminding you
   of something that provides behaviour.

Agreed.

        Enno