Re: Divide Large Class?

From:
Victor Bazarov <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Mon, 23 Feb 2009 15:09:57 -0500
Message-ID:
<gnuvqm$st7$1@news.datemas.de>
Immortal Nephi wrote:

[..]
    My question is ? how can one big class break into smaller sub-
classes. [..]


The answer is "inheritance".

     struct A { int a; void foo_a(); void bar_a(); };
     struct B { double b; void foo_b(); void bar_b(); };
     struct C { char c; void foo_c(); void bar_c(); };

     struct ABC: A, B, C {};

That can be seen as a better alternative to

     struct ABC {
         int a;
         double b;
         char c;

         void foo_a();
         void bar_a();
         void foo_b();
         void bar_b();
         void foo_c();
         void bar_c();
     };

Whether it makes sense or not, it's for the programmer to decide. Of
course the problem with inheriting those classes is that 'A::foo_a' has
no way of getting to the 'C' part (so to speak). So, if it needs to,
you would have to keep them together. A possible alternative is to
extract all data into a separate class, a virtual base to all "parts":

     struct VeryBase { int a; double b; char c; };

     struct A : virtual VeryBase { void foo_a(); void bar_a(); };
     struct B : virtual VeryBase { void foo_b(); void bar_b(); };
     struct C : virtual VeryBase { void foo_c(); void bar_c(); };

     struct ABC: A, B, C {};

V
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