readme.md

Behavioral

Behavioral patterns are concerned with algorithm, the assignment of responsibilities between objects, and the patterns of communication between them. They help to focus on just the way objects are interconnected by shifting focus away from complex control flow that may be difficult to follow at run-time.

Class Patterns

Behavioral class patterns use inheritance to describe algorithms and flow of control:

Name	Varying Aspect	Intent
Interpreter	grammar and interpretration of a language	To define a representation for a languages grammer along with an interpreter that uses the representation to interpret sentences in the language.
Template Method	steps of an algorithm	To 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.

Object Patterns

Behavioral object patterns describe how a group of objects cooperate to perform a task that no single object can carry out alone, and how peer objects know about each other:

Name	Varying Aspect	Intent
Chain of Responsibility	the object that can fulfill a request	To 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	when and how a request is fulfilled	To encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
Iterator	how an aggregate's elements are accessed, traversed	To provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
Mediator	how and which objects interact with each other	To 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	what private information is stored outside an object, and when	To capture and externalize an object's internal state so that the object can be restored to this state later, without breaking encapsulation.
Observer	number of objects that depend on another object; how the dependent objects stay up to date	To define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
State	internal states of an object	To allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
Strategy	an algorithm	To define a family of algorithms, encapsulate each one, and make them interchangable. Strategy also lets the algorithm vary independently from the clients that use it.
Visitor	operations that can be applied to object(s) without changing their class(es)	To request 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.

Summary

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