Pattern for roles ?

[Pho Tek]

Say I have a Person class.
And I have two roles which I want to model:

1. Buyer
   
2. Seller
   

How do you implement this ?
I've tried using interfaces.
e.g.


interface IBuyer{..}
interface ISeller{..}
Person p = new Person();
class Buyer extends Person implements IBuyer{..}
class Seller extends Person implements ISeller{..} 


The problem I see here is that I can't changed my role
dynamically. For example, the program might allow a Person
to assume another role in the middle of the program.
Thanks
Pho

[Junilu Lacar]

Martin Fowler discusses this in his book "Analysis Patterns". You might find some material on his website: http://www.martinfowler.com
Junilu

[Jes Sie]

Originally posted by Pho Tek:
Say I have a [b]Person class.
And I have two roles which I want to model:

1. Buyer
   
2. Seller
   

How do you implement this ?
I've tried using interfaces.
e.g.


interface IBuyer{..}
interface ISeller{..}
Person p = new Person();
class Buyer extends Person implements IBuyer{..}
class Seller extends Person implements ISeller{..} 


The problem I see here is that I can't changed my role
dynamically. For example, the program might allow a Person
to assume another role in the middle of the program.
Thanks
Pho[/B]

This maybe a late reply, but, heh, it's better never.
OK, maybe you can try like this: -
Person has a "1 to 0..*" composition relationship with PersonRole.
Place a Condition on the relationship like "Max 1 each".
PersonRole is an abstract class.
Both Buyer and Seller inherits from PersonRole.
This way, Person can have zero or a max of either Buyer or Seller role.

------------------
Thank you.
- Simon See
[email protected]
-after office hours-
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