Design Patterns
Categories
Creational
Structural
Behavioral
Creational
Abstract Factory
Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
Factory Method
Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.
Builder
Separate the construction of a complex object from its representation so that the same construction process can create different representations.
Separate the construction of a complex object from its representation so that the same construction process can create different representations.
Lazy Initialization
Tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
Object Pool
Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
used to manage the object caching
Prototype
Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this 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.
Highlander, One instance only
Borg, Multiple instances sharing state
Multiton, One instance per key
Utility
A class with a private constructor that contains only static methods.
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.
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.
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.
Compose objects into tree structures to represent whole-part 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.
Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
Facade
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.
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., Simple Interface, Hide complexity
Flyweight
Use sharing to support large numbers of fine-grained objects efficiently.
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.
Provide a surrogate or placeholder for another object to control access to it.
Behavioral
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.
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.
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.
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.
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.
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.
Without violating encapsulation, capture and externalize an object's internal state so that the object can be returned 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.
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 behavior when its internal state changes. The object will appear to change its class.
Allow an object to alter its behavior when its 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.
Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it.
Specification
Recombinable Business logic in a boolean fashion
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.
Define the skeleton of an algorithm in an operation, deferring some steps to client subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure., Concrete Methods, Organizing Methods
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.
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., Single-Serving Visitor, Hierarchical Visitor
Null Object
The intent of a Null Object is to encapsulate the absence of an object by providing a substitutable alternative that offers suitable default do nothing behavior.
Sentinel
The SentinelPattern occurs when a unique value, outside the set of "domain" values, is used to communicate information to and/or from a function or subsystem.
