Behavioral Design Patterns

Question 1

Chain of Responsibility

Answer 1

It avoids attaching the sender of a request to its receiver, giving this way other objects the possibility of handling the request too.
- The objects become parts of a chain and the request is sent from one object to another across the chain until one of the objects will handle it.

Question 2

Command

Answer 2

Encapsulate a request in an object, Allows the parameterization of clients with different requests and Allows saving the requests in a queue.

Question 3

Interpreter

Answer 3

Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language / Map a domain to a language, the language to a grammar, and the grammar to a hierarchical object-oriented design.

Question 4

Iterator

Answer 4

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

Question 5

Mediator

Answer 5

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 6

Observer

Answer 6

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

Question 7

Strategy

Answer 7

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

Question 8

Template Method

Answer 8

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 letting them to change the algorithm’s structure.

Question 9

Visitor

Answer 9

Represents 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 10

Null Object

Answer 10

Provide an object as a surrogate for the lack of an object of a given type. / The Null Object Pattern provides intelligent do nothing behavior, hiding the details from its collaborators.