Re: Inheritance - style question

From:

Paul N <gw7rib@aol.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 20 Nov 2009 08:30:14 -0800 (PST)

Message-ID:

<5f29c999-c0b8-46d1-a246-7d5811baabf8@g23g2000yqh.googlegroups.com>

On 20 Nov, 15:06, "Alf P. Steinbach" <al...@start.no> wrote:

* Paul N:

I'm using inheritance - this particular case is to provide a linked
list of attributes of a piece of text (text colour, italic etc) so
that different parts of it can be shown in different ways.

class Attrib : public Listable {
public:
// stuff including where in the text the attribute starts to take
effect
};

Why not use a std::list.

Because I have already written a linked list class, which works
perfectly well and which I understand how to use, whereas I don't know
anything about templates. Though arguably it would be a good idea for
me to find out :-)

class Col_Attrib : public Attrib {
public:
  COLORREF col;
  // plus more stuff
};

class Ink : public Col_Attrib {
public:
  // stuff
};

class Paper : public Col_Attrib {
public:
  // stuff
};

Now, if I include a constructor:

Col_Attrib::Col_Attrib(COLORREF incol) : col(incol) { }

then this doesn't, by itself, create constructors for Ink and Paper
taking a COLORREF, does it?

No.

If I did want such constructors, would it be best to include a
constructor as above and then do:

Ink::Ink(COLORREF incol) : Col_Attrib(incol) { }

or would it be better to do:

Ink::Ink(COLORREF incol) : col(incol) { }

directly? The first form seems more natural in terms of the hierarchy,
but the second seems more efficient.

The second form wouldn't compile.

Do you mean it won't compile *if I include the above-mentioned
Col_Attrib constructor* or that it won't compile full stop? My
question was intended to include this constructor only in the first
alternative - sorry for the lack of clarity.

Thanks.
Paul.