NEWS

Tuesday, May 18, 2010

GoF patterns summary for reference






























































































































Creational


Abstract Factory


Provide an interface for creating families of related or dependent objects without specifying their concrete classes.


 


Builder


Separate the construction of a complex object from its representation so that the same construction process can create different representations.


 


Factory Method


Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.


 


Prototype


Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.


 


Singleton


Ensure a class only has one instance, and provide a global point of access to it.


 


Structural


Adapter


Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.


 


Bridge


Decouple an abstraction from its implementation so that the two can vary independently.


 


Composite


Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.


 


Decorator


Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.


 


Fa├žade


Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.


 


Flyweight


Use sharing to support large numbers of fine-grained objects efficiently.


 


Proxy


Provide a surrogate or placeholder for another object to control access to it.


 


 


Behavioural


Chain Of Responsibility


Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.


 


Command


Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.


 


Interpreter


Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.


 


Iterator


Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.


 


Mediator


Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.


 


Memento


Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later.


 


Observer


Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.


 


State


Allow an object to alter its behaviour when it’s internal state changes. The object will appear to change its class.


 


Strategy


Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.


 


Template Method


Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.


 


Visitor


Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.


 


 


 

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