The ABC's of Domain Modeling in Delphi [Object Factories]

Created by zope. Last modified 2004-07-15 05:26:36.

Object Factories Hide Concrete Classes

Object Construction -- the Achilles' Heel of ABC Design

Having declared ABC's for all of the related families of subclasses, we have solved all our problems, no? But how do instances of those (now hidden) concrete classes get constructed? Must we re-expose the clients to them?

Object Factories Preserve Encapsulation

Reapplying the idea of "black boxes", we can "package up" the knowledge about the concrete classes into another object, a factory. Clients can then ask the factory to create a concrete class "by name", or using some other well-defined protocol, and remain insulated from the vagaries of the concrete classes.

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