Ruby - Design patterns tdc2011

Design Patterns + Ruby

http://github.com/fellix

@rs_felix

http://www.crafters.com.br @crafterstudio

http://blog.rollingwithcode.com

http://gitub.com/fellix










Por que Ruby?

1995

Erich Gamma, Richard Helm, Raph Johnson, John Vlissides

“Gang of Four”

Design Patterns

Template Method

class Relatorio def generate output_head output_body output_footer end def output_head end def output_body end def output_footer endend



Template Method

class HTMLRelatorio < Relatorio def output_head

puts "<html><head><title>Relatório HTML</title></head>"

end def output_body puts "<body>...</body>" end def output_footer puts "</html>" endend







relatorio = HTMLRelatorio.newrelatorio.generate



class Relatorio def generate output_head output_body output_footer end end


<html> <head><title>...</title></head> <body> ... </body></html>

Strategy

Delegar ao invés de herdar

class Formatter def format(text)

endend

class Formatter def format(text)

raise "Abstract method" endend

class HTMLFormatter < Formatter def format(text)

puts "<html> " puts "<head> " puts "<title>...</title></head> " puts "<body>#{text}</body></html>"

endend

class HTMLFormatter < Formatter def format(text)


endend

class HTMLFormatter def format(text)


endend

class HTMLFormatter def format(text)


endend

Duck Typing

class Relatorio def initialize(formatter)

@formatter = formatter end def generate(text)

@formatter.format(text) endend










Delegate

relatorio = Relatorio.new(HTMLFormatter.new)relatorio.generate("Muitas e muitas coisas")



Observer

Manter-se informado sobre determinadas mudanças em objetos

class NotaFiscal def pagar

... endend

class FluxoCaixa def atualizar

... endend


... endend

Consulta no banco de dados todas as

notas pagas e atualiza o fluxo de

caixa

NotaFiscal FluxoCaixa

pagar

class NotaFiscal def pagar

... endend

class NotaFiscal def pagar (fluxo)

...fluxo.atualizar

endend

class NotaFiscal def initialize (...)

...@observers = []

end def pagar

... endend

class NotaFiscal def add_observer (observer)

@observers << observer end def notify_observers

@observers.each do |o| o.update(self)

end endend


... end def update (nota_fiscal)

... endend

fluxo_caixa = FluxoCaixa.newnota_fiscal = NotaFiscal.newnota_fiscal.add_observer fluxo_caixa

nota_fiscal.pagar

require "observer" class NotaFiscal

include Observable

def pagar...changednotify_observers(self)

endend


include Observable


endend


include Observable


endend


include Observable


endend


include Observable


endend

@changed = true


include Observable


endend

@observers.each { |o| o.update(object) } if @changed


... end def update (nota_fiscal)

... endend


nota_fiscal.pagar


nota_fiscal.pagar

nota_fiscal fluxo_caixa

notifica

Factory

Fornecer uma interface para a criação de objetos, sem especificar a classe concreta

HTMLReader.new

PDFReader.new

class ReaderFactory def initialize (format)

@reader_class = self.class.const_get("#{format}Reader")

end def reader

@reader_class.new endend



end def reader




end def reader




end def reader


html_reader = ReaderFactory.new("HTML").reader

pdf_reader = ReaderFactory.new("PDF").reader

class ReaderFactory def self.pdf_reader

ReaderFactory.new("PDF").reader end def self.html_reader

ReaderFactory.new("HTML").reader endend

html_reader = ReaderFactory.html_reader

Active Record Factory

class Base ...

end

class Base def self.mysql_connection

... endend

class Base def self.postgresql_connection

... endend

adapter = "mysql"method_name = "#{adapter}_connection"Base.send(method_name, config)

Builder

Criar objetos complexos de forma legível, passo a passo

class Pizza attr_accessor :massa, :molho, :coberturaend

class PizzaBuilder attr_reader :pizza def initialize

@pizza = Pizza.new endend

class CalabresaBuilder < PizzaBuilder def molho

@pizza.molho = "Tomate" end def massa

@pizza.massa = "Pão" end def cobertura

@pizza.cobertura = "queijo, calabresa" endend

builder = CalabresaBuilder.newbuilder.molhobuilder.coberturabuilder.massapizza = builder.pizza

pizza = CalabresaBuilder.new.molho.cobertura.massa.pizza

class CalabresaBuilder < PizzaBuilder def molho

@pizza.molho = "Tomate"self

end def massa

@pizza.massa = "Pão"self

end def cobertura

@pizza.cobertura = "queijo, calabresa"self

endend

builder = CalabresaBuilder.newbuilder.molho_and_coberturapizza = builder.pizza

class PizzaBuilder def method_missing(name, *args)

methods = name.to_s.split("_")return super(name, *args) unless methods[1] == "and"

methods.each do |method|next if method == "and"send(method)

end

endend

builder.molho_and_cobertura

builder.massa_and_cobertura

builder.molho_and_cobertura_and_massa

Adapter

Conectar objetos que não tem uma interface comum

class Padrao1 def conectar (cabo)

cabo.energizar endend


cabo.energizar endend

class CaboPadrao1 def energizar

... endend


cabo.executar endend


cabo.executar endend

class CaboPadrao2 def executar

... endend


... endend


... endend

tomada = Padrao2.newtomada.conectar CaboPadrao2.new


... endend



... endend


class AdapterPadrao2 def initialize(cabo_padrao2)

@cabo = cabo_padrao2 end def energizar

@cabo.executar endend







adapter = AdapterPadrao2.new(CaboPadrao2.new)tomada = Padrao1.newtomada.conectar(adapter)



tomada adapter cabo

Proxy

class ContaBancaria def initialize(saldo)

@saldo = saldo end def depositar!(valor)

@saldo += valor end def sacar!(valor)

@saldo -= valor end def some_method endend

class ContaBancariaProxy def initialize(conta_bancaria)

@conta_bancaria = conta_bancaria end def depositar!(valor)

@conta_bancaria.depositar! valor end def sacar!(valor)

@conta_bancaria .sacar! valor endend

Protection Proxy

class ContaBancariaProxy def initialize(conta_bancaria)

@conta_bancaria = conta_bancaria end def depositar!(valor)

@conta_bancaria.depositar! valor end def sacar!(valor)


class ContaBancariaProxy def initialize(conta_bancaria, owner)

@conta_bancaria = conta_bancaria@owner = owner

end protected def check_access

raise "Illegal Access" unless User. login == @owner

endend

class ContaBancariaProxy def depositar!(valor) check_access

@conta_bancaria.depositar! valor end def sacar!(valor) check_access


Decorator

class Coffee def price

@price end def ingredients

@ingredients endend

class MilkDecorator def initialize (coffee)

@coffee = coffee end def price

coffee.price + 0.5 end def ingredients

coffee.ingredients + ", Leite" endend













coffee = Coffee.new(1.5, "Café, Água")puts coffee.ingredients

coffee = Coffee.new(1.5, "Café, Água")puts coffee.ingredients Café, Água

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredientsputs coffee.price

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredientsputs coffee.price

Café, Água, Leite

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredientsputs coffee.price 2.0

class ChocolateDecorator def initialize (coffee)



coffee.ingredients + ", Chocolate" endend

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeeputs coffee.ingredients


Café, Água, Chocolate


coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffee

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeecoffee = MilkDecorator.new coffee

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeecoffee = MilkDecorator.new coffeeputs coffee.ingredients

Café, Água, Chocolate, Leite

Singleton

Garantir que só haja uma instancia de determinado objeto

@count

@count@@count

class CountTester @@count = 0 def initialize

@count = 0 end def self.increment

@@count++ end def increment

@count++ endend




@count++ endend

Variável Global




@count++ endend

Variável Local




@count++ endend

Metódo Estático




@count++ endend

Metódo de Instância

class CountTester COUNT = 0end

Variável Global

class Logger @@instance = Logger.new

def self.instance@@instance

endend

logger1 = Logger.instancelogger2 = Logger.instance

logger = Logger.new



end

end



end

private_class_method :newend

require "singleton"class Logger

include Singletonend

logger = Logger.new

logger = Logger.new

private method ‘new’ called for Logger::Class

logger = Logger.instance

Obrigado

http://github.com/fellix

@rs_felix

http://www.crafters.com.br @crafterstudio












Technology

Ruby - Design patterns tdc2011