Inheritance question

I have an instance where I have a Base Abstract Class, and 4 Derived
classes. I now need to make a list class that will store the objects. My
question is how do I go about creating the list class...I am assuming it
should be a standalone class that uses an arraylist to store the objects.
If I go that route how do I instantiate the objects so they get added to
the list of objects, and how do I know what type they are when iterating
through the list of objects? Or am I way off base (Pun Intended)?

"RSH" <way_beyond_oops@yahoo.comwrote in message
news:OFR4O1CiHHA.2140@TK2MSFTNGP05.phx.gbl...>
Not enough information, IMHO.
>
For example, what is in your ChildListClass that you want to do that
prevents you from using (for example) a generic List<Tclass or a
Collection of some sort? Do you actually want your derived instances
automatically added to the list? That's not what your example code
appears to do.
>
As far as getting the type of the instances, you can use the GetType()
method on any object to get its type. Compare it to a specific type if
you want to know whether that object is in fact that type. Alternatively,
you can use the "is" and "as" keywords to compare types or cast types
respectively. They are slightly different, in that if a conversion from
one type to another exists, they will treat two things as the same type.
If you know that no conversion to your target type exists for other
objects, or if having such a conversion is okay, then that might be the
way to go.
>
Pete

I am working on some general OOP constructs and I was wondering if I could
get some guidance.
>
I have an instance where I have a Base Abstract Class, and 4 Derived
classes. I now need to make a list class that will store the objects. My
question is how do I go about creating the list class...I am assuming it
should be a standalone class that uses an arraylist to store the objects.
If I go that route how do I instantiate the objects so they get added to the
list of objects, and how do I know what type they are when iterating through
the list of objects? Or am I way off base (Pun Intended)?

Peter,
>
Thanks for the reply. Sorry about that.
>
I do want to have the objects to be added to the list on instantiation...I
just didn't know how to represent that.

class BaseClass
{
static private List<BaseClass_grbcInstances;
>
public BaseClass()
{
_grbcInstances.Add(this);
}
>
public void Remove()
{
_grbcInstances.Remove(this);
}
}

"RSH" <way_beyond_oops@yahoo.comwrote in message
news:eCNsYLDiHHA.1216@TK2MSFTNGP03.phx.gbl...>
There are a number of ways to implement something like that. Without
knowing more about your specific intent, preferences, etc. I can't offer
advice on a particular implementation to choose. However, here's one
example of doing what you want:
>
class BaseClass
{
static private List<BaseClass_grbcInstances;
>
public BaseClass()
{
_grbcInstances.Add(this);
}
>
public void Remove()
{
_grbcInstances.Remove(this);
}
}
>
The BaseClass can then provide methods for manipulating, searching, etc.
the list of objects. Note that you need to provide an explicit "Remove"
method to ensure that objects are actually released when you want them to
be. This puts the onus on you to figure out when you're actually done
with an object, at least as it relates to the master list of objects. I
have seen mentions of something called a "weak reference" that may or may
not help you around this issue; I don't know enough about weak references
to offer you advice on that.
>
Finally, I agree with Jon's statement about the possibility of using
virtual methods to deal with per-type behaviors. It's unusual to need to
know the actual type of an object and while I took the shortcut of simply
answering the direct question you asked, I agree that it's more likely
that whatever reason you think you need the type for, that can be more
properly addressed using virtual methods.
>
Pete

Hi,
>
I am working on some general OOP constructs and I was wondering if I could
get some guidance.

>
I have an instance where I have a Base Abstract Class, and 4 Derived
classes. I now need to make a list class that will store the objects. My
question is how do I go about creating the list class...I am assuming it
should be a standalone class that uses an arraylist to store the objects.
If I go that route how do I instantiate the objects so they get added to

list of objects, and how do I know what type they are when iterating

the list of objects? Or am I way off base (Pun Intended)?
>

I guess I did need to be a lot clearer on intent. Lets assume that my
base class is a Person Class. The derived classes are
Employee,Customer,Vendor.
I was attempting to create a list of Persons which I figured would
probably be a static collection in the base class. But after thinking
about it a bit more would it make more sense to have a static collection
in each derived class that holds only objects of the appropriate type?

I am trying to learn inheritance so i dont really know the questions to
ask. I am just trying to sort through handling a one to many relationship
when inheritance is involved.