Ruby - Design patterns tdc2011

@rs_felix

http://github.com/fellix

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

http://blog.rollingwithcode.com

Erich Gamma, Richard Helm,
Raph Johnson, John Vlissides

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

class Relatorio
def generate
output_head
Template
output_body
Method
output_footer
end
def output_head
end
def output_body
end
def output_footer
end
end

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>"
end
end

relatorio = HTMLRelatorio.new
relatorio.generate

class Relatorio
def generate
output_head
relatorio.generate
output_body
output_footer
end
end

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

class Formatter
def format(text)

end
end

class Formatter
def format(text)
raise "Abstract method"
end
end

class HTMLFormatter < Formatter
def format(text)
puts "<html> "
puts "<head> "
puts "<title>...</title></head> "
puts "<body>#{text}</body></html>"
end
end

class HTMLFormatter
def format(text)
puts "<html> "
puts "<head> "
end
end

Duck Typing
class HTMLFormatter
def format(text)
puts "<html> "
puts "<head> "
end
end

class Relatorio
def initialize(formatter)
@formatter = formatter
end
def generate(text)
@formatter.format(text)
end
end

class Relatorio
def initialize(formatter)
@formatter = formatter Delegate
end
def generate(text)
@formatter.format(text)
end
end

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

Manter-se informado sobre determinadas mudanças em
objetos

class NotaFiscal
def pagar
...
end
end

class FluxoCaixa
def atualizar
...
end
end

Consulta no banco
class FluxoCaixa
de dados todas as
def atualizar
notas pagas e
...
atualiza o ﬂuxo de
end
caixa
end

pagar

NotaFiscal FluxoCaixa

class NotaFiscal
def pagar (ﬂuxo)
...
ﬂuxo.atualizar
end
end

class NotaFiscal
def initialize (...)
...
@observers = []
end
def pagar
...
end
end

class NotaFiscal
def add_observer (observer)
@observers << observer
end
def notify_observers
@observers.each do |o|
o.update(self)
end
end
end

class FluxoCaixa
def atualizar
...
end
def update (nota_ﬁscal)
...
end
end

fluxo_caixa = FluxoCaixa.new
nota_fiscal = NotaFiscal.new
nota_fiscal.add_observer fluxo_caixa

nota_fiscal.pagar

require "observer"
class NotaFiscal
include Observable

def pagar
...
changed
notify_observers(self)
end
end

require "observer"
class NotaFiscal
include Observable

def pagar @changed = true
...
changed
end
end

require "observer"
class NotaFiscal
include Observable

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

notifica

nota_fiscal
fluxo_caixa = FluxoCaixa.new fluxo_caixa
nota_fiscal = NotaFiscal.new
nota_fiscal.add_observer fluxo_caixa

nota_fiscal.pagar

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

class ReaderFactory
def initialize (format)
@reader_class =
self.class.const_get("#{format}Reader")
end
def reader
@reader_class.new
end
end

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
end
end

html_reader = ReaderFactory.html_reader

class Base
def self.mysql_connection
...
end
end

class Base
def self.postgresql_connection
...
end
end

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

Criar objetos complexos de forma legível, passo a passo

class Pizza
attr_accessor :massa, :molho, :cobertura
end

class PizzaBuilder
attr_reader :pizza
def initialize
@pizza = Pizza.new
end
end

class CalabresaBuilder < PizzaBuilder
def molho
@pizza.molho = "Tomate"
end
def massa
@pizza.massa = "Pão"
end
def cobertura
@pizza.cobertura = "queijo, calabresa"
end
end

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

builder = CalabresaBuilder.new
builder.molho_and_cobertura
pizza = 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

end
end

builder.molho_and_cobertura_and_massa

Conectar objetos que não tem uma interface comum

class Padrao1
def conectar (cabo)
cabo.energizar
end
end

class CaboPadrao1
def energizar
...
end
end

class Padrao2
def conectar (cabo)
cabo.executar
end
end

class CaboPadrao2
def executar
...
end
end

class CaboPadrao2
def executar
tomada = Padrao2.new
...
tomada.conectar
end
CaboPadrao2.new
end

class CaboPadrao2
def executar
...
tomada.conectar
end
CaboPadrao2.new
end

class AdapterPadrao2
def initialize(cabo_padrao2)
@cabo = cabo_padrao2
end
def energizar
@cabo.executar
end
end

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

tomada adapter cabo
adapter = AdapterPadrao2.new(CaboPadrao2.new)
tomada.conectar(adapter)

class ContaBancaria
def initialize(saldo)
@saldo = saldo
end
def depositar!(valor)
@saldo += valor
end
def sacar!(valor)
@saldo -= valor
end
def some_method
end
end

class ContaBancariaProxy
def initialize(conta_bancaria)
@conta_bancaria = conta_bancaria
end
@conta_bancaria.depositar! valor
end
def sacar!(valor)
@conta_bancaria .sacar! valor
end
end

def initialize(conta_bancaria, owner)
@conta_bancaria = conta_bancaria
@owner = owner
end

protected
def check_access
raise "Illegal Access" unless User. login
== @owner
end
end

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

class Coffee
def price
@price
end
def ingredients
@ingredients
end
end

class MilkDecorator
def initialize (coffee)
@coffee = coffee
end
def price
coffee.price + 0.5
end
def ingredients
coffee.ingredients + ", Leite"
end
end

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

puts coffee.ingredients Café, Água

coffee = MilkDecorator.new coffee
puts coffee.price

puts coffee.ingredients Café, Água, Leite
puts coffee.price

puts coffee.price 2.0

class ChocolateDecorator
def initialize (coffee)
@coffee = coffee
end
def price
coffee.price + 1.0
end
def ingredients
coffee.ingredients + ", Chocolate"
end
end

coffee = ChocolateDecorator.new coffee

Café, Água,
puts coffee.ingredients Chocolate

Café, Água,
Chocolate, Leite

Garantir que só haja uma instancia de determinado objeto

class CountTester
@@count = 0
def initialize
@count = 0
end
def self.increment
@@count++
end
def increment
@count++
end
end

class CountTester
Variável
@@count = 0
Global
def initialize
@count = 0
end
def self.increment
@@count++
end
def increment
@count++
end
end

class CountTester
@@count = 0
def initialize
Variável
@count = 0
Local
end
def self.increment
@@count++
end
def increment
@count++
end
end

class CountTester
@@count = 0
def initialize
@count = 0
end
Metódo
def self.increment
Estático
@@count++
end
def increment
@count++
end
end

class CountTester
@@count = 0
def initialize
@count = 0
end
def self.increment
@@count++
end
Metódo de
def increment
Instância
@count++
end
end

class CountTester
Variável
COUNT = 0
Global
end

class Logger
@@instance = Logger.new

def self.instance
@@instance
end
end

logger1 = Logger.instance
logger2 = Logger.instance

class Logger

def self.instance
@@instance
end

end

class Logger

def self.instance
@@instance
end

private_class_method :new
end

require "singleton"
class Logger
include Singleton
end

logger = Logger.new

private method ‘new’
called for Logger::Class

Obrigado
@rs_felix

http://github.com/fellix

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

http://blog.rollingwithcode.com

Ruby - Design patterns tdc2011

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