OO Design question

[Kalpesh]

Hello All,

Please help validate this design problem

Assume that I have several entities in my project (eg Supplier,
Customer etc).
All of them save several common properties - name, address, city,
state, zipcode etc

I thought of making a base class - BusinessEntity (with all of the
above properties)
Then, create Supplier/Customer class which derives from BusinessEntity
& have their own specialized behaviour.

Is this approach valid ?

Also, can a class be made base class solely on the basis of common
data, that it can hold ?
In my example, there is no point repeating (name, address...) in
Supplier, Customer
Hence, I think of creating BusinessEntity with all the above properties
So, is it valid to have base class with only data & no behaviour
(methods) ?
I would love to hear arguments in favour/against of the above approach

Cheers
Kalpesh

[Jeff Louie]

KJ...With .NET 2.0 you can implement delegation using generics!

using System;
using System.Collecti ons.Generic;
using System.Text;

namespace GenericMI
{
// first we create the abstractions
public interface I1
{
void SayHello();
}
public interface I2
{
int GetValue();
}
public interface IProgram : I1, I2 { }

// second we write the concrete classes that implement the
abstractions
public class Implementation1 : I1
{
public void SayHello()
{
Console.WriteLi ne("Hello.");
}
}
public class Implementation2 : I2
{
private int i = 1;
public int GetValue()
{
return i;
}
}
// finally we write the wrapper class that contains
// the concrete classes
public class GenericMI<T1, T2> : IProgram where T1 : class, I1,
new()
where T2: class,I2, new()
{
private T1 pimplI1= new T1();
private T2 pimplI2 = new T2();
// we forward calls to the contained object
public void SayHello()
{
pimplI1.SayHell o();
}
public int GetValue()
{
return pimplI2.GetValu e();
}
}
class Program
{
static void Main(string[] args)
{
GenericMI<Imple mentation1,Impl ementation2> mi=
new GenericMI<Imple mentation1,Impl ementation2>();
mi.SayHello();
Console.WriteLi ne(mi.GetValue( ));
Console.ReadLin e();
}
}
}

Regards,
Jeff

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[Kalpesh]

Hi Everyone,

Although the discussion digressed a little, I got to see different view
points

Bruce, I liked your design :)
John - I will be reading the open-closed principle

I think, it requires great amount of understanding of domain (context),
before designing classes. So, making something base class, based on
common data - MIGHT not be a good idea.

Also, if I make address as part of BusinessEntity, it is kind of a
closed design
However, good discussion helps see different perspective

Thank you everyone & happy x'mas
Kalpesh

[john_teague]

Real Quick, paraphrased Open-Closed principle means "Open for
extensibility, closed for modifications" This means that if you need
to add functionality to a system you do it by writing new code and not
modifiy existing code. Making address part of BusinessEntity is the
opposite of what I'm talking about if there is different functionality
associated with address data.

Good Luck.

[Kalpesh]

Thank you everyone for your views

Kalpesh

[Dave Johnson]

would u please show the Aggregation instead of inheritance in code.

you seem you have experiance doing it before which many coder and i am
one of them didnt encounter the need to do it yet.

would be very please to see any simple code explaining it

Thanks a lot

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