Abstract Factory em Ruby
O Abstract Factory é um padrão de projeto criacional, que resolve o problema de criar famílias inteiras de produtos sem especificar suas classes concretas.
O Abstract Factory define uma interface para criar todos os produtos distintos, mas deixa a criação real do produto para classes fábrica concretas. Cada tipo de fábrica corresponde a uma determinada variedade de produtos.
O código cliente chama os métodos de criação de um objeto fábrica em vez de criar produtos diretamente com uma chamada de construtor (usando operador new). Como uma fábrica corresponde a uma única variante de produto, todos os seus produtos serão compatíveis.
O código cliente trabalha com fábricas e produtos somente através de suas interfaces abstratas. Ele permite que o mesmo código cliente funcione com produtos diferentes. Você apenas cria uma nova classe fábrica concreta e a passa para o código cliente.
Se você não conseguir descobrir a diferença entre os padrões Factory, Factory Method e Abstract Factory, leia nossa Comparação Factory.
Complexidade:
Popularidade:
Exemplos de uso: O padrão Abstract Factory é bastante comum no código Ruby. Muitas frameworks e bibliotecas o utilizam para fornecer uma maneira de estender e personalizar seus componentes padrão.
Identificação: O padrão é fácil de reconhecer pelos seus métodos, que retornam um objeto fárica. Em seguida, a fábrica é usado para criar subcomponentes específicos.
Exemplo conceitual
Este exemplo ilustra a estrutura do padrão de projeto Abstract Factory. Ele se concentra em responder a estas perguntas:
- De quais classes ele consiste?
- Quais papéis essas classes desempenham?
- De que maneira os elementos do padrão estão relacionados?
main.rb: Exemplo conceitual
# The Abstract Factory interface declares a set of methods that return different
# abstract products. These products are called a family and are related by a
# high-level theme or concept. Products of one family are usually able to
# collaborate among themselves. A family of products may have several variants,
# but the products of one variant are incompatible with products of another.
class AbstractFactory
# @abstract
def create_product_a
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# @abstract
def create_product_b
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Factories produce a family of products that belong to a single
# variant. The factory guarantees that resulting products are compatible. Note
# that signatures of the Concrete Factory's methods return an abstract product,
# while inside the method a concrete product is instantiated.
class ConcreteFactory1 < AbstractFactory
def create_product_a
ConcreteProductA1.new
end
def create_product_b
ConcreteProductB1.new
end
end
# Each Concrete Factory has a corresponding product variant.
class ConcreteFactory2 < AbstractFactory
def create_product_a
ConcreteProductA2.new
end
def create_product_b
ConcreteProductB2.new
end
end
# Each distinct product of a product family should have a base interface. All
# variants of the product must implement this interface.
class AbstractProductA
# @abstract
#
# @return [String]
def useful_function_a
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Products are created by corresponding Concrete Factories.
class ConcreteProductA1 < AbstractProductA
def useful_function_a
'The result of the product A1.'
end
end
class ConcreteProductA2 < AbstractProductA
def useful_function_a
'The result of the product A2.'
end
end
# Here's the the base interface of another product. All products can interact
# with each other, but proper interaction is possible only between products of
# the same concrete variant.
class AbstractProductB
# Product B is able to do its own thing...
def useful_function_b
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# ...but it also can collaborate with the ProductA.
#
# The Abstract Factory makes sure that all products it creates are of the same
# variant and thus, compatible.
def another_useful_function_b(_collaborator)
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Products are created by corresponding Concrete Factories.
class ConcreteProductB1 < AbstractProductB
# @return [String]
def useful_function_b
'The result of the product B1.'
end
# The variant, Product B1, is only able to work correctly with the variant,
# Product A1. Nevertheless, it accepts any instance of AbstractProductA as an
# argument.
def another_useful_function_b(collaborator)
result = collaborator.useful_function_a
"The result of the B1 collaborating with the (#{result})"
end
end
class ConcreteProductB2 < AbstractProductB
# @return [String]
def useful_function_b
'The result of the product B2.'
end
# The variant, Product B2, is only able to work correctly with the variant,
# Product A2. Nevertheless, it accepts any instance of AbstractProductA as an
# argument.
def another_useful_function_b(collaborator)
result = collaborator.useful_function_a
"The result of the B2 collaborating with the (#{result})"
end
end
# The client code works with factories and products only through abstract types:
# AbstractFactory and AbstractProduct. This lets you pass any factory or product
# subclass to the client code without breaking it.
def client_code(factory)
product_a = factory.create_product_a
product_b = factory.create_product_b
puts product_b.useful_function_b
puts product_b.another_useful_function_b(product_a)
end
# The client code can work with any concrete factory class.
puts 'Client: Testing client code with the first factory type:'
client_code(ConcreteFactory1.new)
puts "\n"
puts 'Client: Testing the same client code with the second factory type:'
client_code(ConcreteFactory2.new)
output.txt: Resultados da execução
Client: Testing client code with the first factory type:
The result of the product B1.
The result of the B1 collaborating with the (The result of the product A1.)
Client: Testing the same client code with the second factory type:
The result of the product B2.
The result of the B2 collaborating with the (The result of the product A2.)
