Sunday, May 29, 2011

Difference between Factory Pattern or Abstract Factory Pattern and Builder Pattern

Abstract factory may also be used to construct a complex object, then what is the difference with builder pattern? In builder pattern emphasis is on ‘step by step’. Builder pattern will have many number of small steps. Those every steps will have small units of logic enclosed in it. There will also be a sequence involved. It will start from step 1 and will go on upto step n and the final step is returning the object. In these steps, every step will add some value in construction of the object. That is you can imagine that the object grows stage by stage. Builder will return the object in last step. But in abstract factory how complex the built object might be, it will not have step by step object construction.

Both are creational pattern but differ:
Factory Pattern Builder Pattern
The factor pattern defers the choice of what concrete type of object to
make until run time.
E.g. going to a restaurant to order the special of  the day.  The waiter is the interface to the factory that takes the
abstractor generic message "Get me the special of the day!" and returns
the concrete product (i.e "Chilli Paneer" or some other dish.)
The builder pattern encapsulates the logic of how to put together a
complex object so that the client just requests a configuration and the
builder directs the logic of building it.   E.g The main contractor
(builder) in building a house knows, given a floor plan, knows how to
execute the sequence of operations (i,e. by delegating to subcontractors)
needed to build the complex object.  If that logic was not encapsulated in
a builder, then the buyers would have to organize the subcontracting
The factory is concerned with what is made. The builder with how it is
made. So it focuses on the steps of constructing the complex object.
In case of Factory or Abstract Factory, the product gets returned immediately Builder returns the product as
the final step.

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