Proxy pattern - Structural

• Use a simple object to represent a complex one
• provides a "Placeholder" for an object to control references to it 
• A class represents functionality of another class
• Creates object having original object to interface its functionality

       

     

Where to use ?

• If creating an object is too expensive in time or memory
• Postpone the creation until you need the actual object
• Load a large image (time consuming)
• Load a remote object over network during peak periods
• Access right is required to a complex system

Implementation example

Concrete class BankAccount implementing interface Account

BankAccount fetching details from banking system

Another class ProxyAccount also implementing same interface Account

ProxyAccount maintaining an object of BankAccount , and returning, if already loaded.

If it doesn’t exists, create BankAccount (real) object which is maintained.