GOF Design Patterns

Summary

Memorize the Gang of Four (i.e. GoF) Design Patterns.

Category of Pattern

Pattern (memorize)	Category (memorize)
Command	Behavioral
Builder	Creational
Adapter	Structural
Interpreter	Behavioral
Template Method	Behavioral
Prototype	Creational
Visitor	Behavioral

More

Pattern (memorize)	Category (memorize)
Iterator	Behavioral
Singleton	Creational
Chain of Responsibility	Behavioral
Bridge	Structural
Mediator	Behavioral
Abstract Factory	Creational
Composite	Structural
Decorator	Structural

More

Pattern (memorize)	Category (memorize)
Factory Method	Creational
Facade	Structural
Memento	Behavioral
State	Behavioral
Strategy	Behavioral
Flyweight	Structural
Observer	Behavioral
Proxy	Structural

Memorize together

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Patterns in Category

Category (memorize)	Patterns (memorize)
List the "Creational" design patterns	- Abstract Factory - Builder - Factory Method - Prototype - Singleton
List the "Structural" design patterns	- Adapter - Bridge - Composite - Decorator - Facade - Flyweight - Proxy
List the "Behavioral" design patterns	- Chain of Responsibility - Command - Interpreter - Iterator - Mediator - Memento - Observer - State - Strategy - Template Method - Visitor

Creational

Pattern (memorize)	Description (memorize)
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.
List the collaborations involved with using "Builder"	- 1. Client creates a "Director" and a "Concrete Builder" instance (a "Builder" subclass for a particular representation), passing the latter to the former. - 2. Client tells the Director to construct the object. - 3. Director directs Builder to build an object (the "Product") by calling its methods. - 4. Client gets Product from Builder subclass instance.
Factory Method	Define an interface for creating an object, but let subclasses decide which class to instantiate. 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 has only one instance and provide a global point of access to it.

Structural

Pattern (memorize)	Description (memorize)
Adapter	Convert the interface of a class into another interface that clients expect. Lets classes work together that couldn't otherwise because of incompatible interface.
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. Lets clients treat individual objects and compositions of objects uniformly.
Decorator	Attach flexible additional responsibilities to an object dynamically. They provide a flexible alternative to subclassing for extending functionality.
Facade	Provide a unified interface to a set of interfaces in a subsystem. 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.

Behavioral

Pattern (memorize)	Description (memorize)
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 undo operations.
Interpreter	Given a language, define a representation for its grammar, along with a system that uses the representation to interpret sentences in the language.
Iterator	Provide a way to access the elements of an aggregate object sequentially with out exposing its underlying implementation.
Mediator	Define an object that encapsulates how a set of objects interact. Promotes loose coupling by keeping objects from referring to each other explicitly, and lets you vary their interaction independently.
Memento	Without violating encapsulation, capture and externalize an object's internal state so that objects can be restored to this state later.
Observer	Define a one-to-many dependency 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.
Strategy	Define a family of algorithms, encapsulate each one, and make them interchangeable. Lets the algorithm vary independently from the clients that use it.
Template Method	Define the skeleton of an algorithm in an operation, deferring some steps to its subclasses. Lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.
Visitor	Represent an operation to be performed on elements of an object structure. Lets you define a new operation without changing the classes of the elements on which it operates.