Software Patterns, Behavioral

Question 1

-Blackboard

Answer 1

Generalized observer, which allows multiple readers and writers. Communicates information system-wide.

Question 2

Chain of responsibility

Answer 2

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.

Question 3

Command

Answer 3

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

Question 4

-Interpreter

Answer 4

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

Question 5

Iterator

Answer 5

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

Question 6

Mediator

Answer 6

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.

Question 7

Memento

Answer 7

Without violating encapsulation, capture and externalize an object’s internal state allowing the object to be restored to this state later.

Question 8

-Null object

Answer 8

Avoid null references by providing a default object.

Question 9

Observer or Publish/subscribe

Answer 9

Define a one-to-many dependency between objects where a state change in one object results in all its dependents being notified and updated automatically.
Allows objects to be notified when state changes.

Question 10

-Servant

Answer 10

Define common functionality for a group of classes

Question 11

-Specification

Answer 11

Recombinable business logic in a Boolean fashion

Question 12

State

Answer 12

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.

Question 13

Strategy

Answer 13

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

Question 14

Template method

Answer 14

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.

Question 15

Visitor

Answer 15

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.

Question 16

Compound Patterns

Answer 16

Combines 2 or more patterns to solve a general or recurring problem. example, MVC