Re: design opinions requested

"Daniel T." <>
Sun, 03 Jun 2007 19:36:14 GMT
Tim H <> wrote:

I have a design opinion. I have 3 models in mind, and I don't
particularly like them, so maybe someone can suggest or help justify.

I have a set of essentially unrelated classes (about 6).

        class Foo;
        class Bar;
        class Bat;

I have a container-ish class that holds many of those other classes
and other meta-data:

        class Stuff {
                vector<pair<string, Foo *> > foos;
                vector<pair<string, Bar *> > bars;
                vector<pair<string Bat *> > bats;

So here's the problem. I need to store the unrelated classes in a
somewhat related way. I need to sort them all together in insert
order, for later retrieval. What I mean is that later, I need to walk
the container somehow and pull out al the Foos, Bars, and Bats,
intermingled with each other, in the order they were inserted.

So, I have dreamed up three answers, none of which I really like.

1) Make a generic base class, Stuff_Item, which is a base class for
Foo, Bar, Bat, etc. Store all Foo, Bar, Bat in a single vector.
Stuff_Item::stuff_type() returns and enum that callers use to
determine the type of the thing held. Callers then up-cast.

2) Make a generic base class, Stuff_Item, which is not a base class,
and which has methods stuff_type() and stuff_index(). stuff_type
returns an enum that callers use to determine the type of the thing
held. stuff_index returns an index (or an iterator) into a type-
specific vector. Keep a seperate vector of Stuff_Items. Callers can
then use that as a (database-style) index.

3) Make a Stuff::Item inner class, which holds an enum of pointers to
Foo, Bar, Bat.. That inner class exposes is_foo(), is_bar(), is_bat()
methods, and get_foo(), get_bar(), get_bat() methods. Just store one
vector of Stuff::Item.

Thoughs, justifications, other ideas?

I'd have to see how the Stuff class is used to figure the best

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