OOP: Princípios e Padroes

Orientação a ObjetosPrincípios e Padrões

Quem sou eu?‣ Programador no Glio

‣ Trabalhei na Dafiti, Emprego Ligado e Tripda

‣ Não mexo com PHP faz exatamente 1 ano

‣ Ruby

‣ @nelson_senna

Agenda

‣ Uma breve introdução a OOP

‣ Os primos pobres do S.O.L.I.D

‣ Padrões de projeto (GoF)

O que é Orientação a Objetos?

O método é apoiado por quatro pilares

Abstração

AbstraçãoOnde podemos errar?

“If a precondition is violated, this means that a client has not satisfied its part of

the bargain, and hence the server cannot proceed reliably. Similarly, if a postcondition is violated, this means

that a server has not carried out its part of the contract, and so its clients can no longer trust the behavior of the server.”

Grady Booch

Encapsulamento

EncapsulamentoOnde podemos errar?

“No part of a complex system should depend on the internal details of any

other part”

Ingalls, D.

Modularidade

ModularidadeOnde podemos errar?

“The overall goal of the decomposition into modules is the reduction of

software cost by allowing modules to be designed and revised independently....

Each module's structure should be simple enough that it can be

understood fully;”

Britton and Parnas

Hierarquia

HierarquiaOnde podemos errar?

“Inheritance makes it possible to define new software in the same way we

introduce any concept to a newcomer, by comparing it with something that is

already familiar”

Cox, B.

O que é um objeto?

Propriedades de um objeto

‣ Estado

‣ Comportamento

‣ Identidade

“The state of an object encompasses all of the (usually static) properties of the

object plus the current (usually dynamic) values of each of these properties.”

Grady Booch

“The state of an object represents the cumulative results of its behavior.”

Grady Booch

“Assim como átomos podem existir repetidas vezes, a identidade possibilita

que múltiplas instâncias possam coexistir.”

Um troxa aí

Objetos não são sacos de dados!

Princípios

Least Astonishment

Command Query Separation

Tell don’t ask

Law of Demeter

Padrões

Decorator

Strategy

Chain of Responsibility

Composite

Template Method

Facade

Dúvidas?

Avalie a palestra!

Lista de imagens‣ Builders: https://flic.kr/p/mjweU

‣ Ikebana: https://flic.kr/p/6P7McX

‣ Boundary: https://flic.kr/p/3QrzLy

‣ Modularity: https://flic.kr/p/9sdBqQ

‣ Hierarchy: https://flic.kr/p/fgGtcP

‣ Objects: https://flic.kr/p/AD4FMh

Referências‣ Tell don’t ask: https://pragprog.com/articles/tell-dont-ask

‣ OOP: Object-Oriented Analysis and Design with Applications - Grady Booch et al

‣ Law of Demeter: http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/paper-boy/demeter.pdf

‣ CQS: http://martinfowler.com/bliki/CommandQuerySeparation.html

‣ Least Astonishment: http://c2.com/cgi/wiki?PrincipleOfLeastAstonishment

‣ Design Patterns: Design Patterns: Elements of Reusable Object-Oriented Software - Gamma et al

‣ Decorator: https://8thlight.com/blog/doug-bradbury/2016/07/18/not-a-decorator-ruby.html

‣ Template Method: https://medium.com/ruby-on-rails/what-i-learned-from-sandi-metz-9d0c94347b7f#.2y8u1prb4