Fabrique en Ruby
La Fabrique est un patron de conception de création qui permet de créer des produits sans avoir à préciser leurs classes concrètes.
La fabrique définit une méthode qui doit être utilisée pour créer des objets à la place de l’appel au constructeur (opérateur new). Les sous-classes peuvent redéfinir cette méthode pour modifier la classe des objets qui seront créés.
Lisez notre Comparaison des fabriques si vous avez du mal à saisir la différence entre les divers concepts et patrons.
Complexité :
Popularité :
Exemples d’utilisation : La fabrique est très largement utilisée en Ruby. Elle est très utile lorsque vous avez besoin de flexibilité dans votre code.
Identification : La fabrique peut être reconnue grâce à ses méthodes de création qui produisent des objets depuis les classes concrètes, mais les retournent en tant qu’objets d’interface ou de type abstrait.
Exemple conceptuel
Dans cet exemple, nous allons voir la structure du patron de conception Fabrique. Nous allons répondre aux questions suivantes :
- Que contiennent les classes ?
- Quels rôles jouent-elles ?
- Comment les éléments du patron sont-ils reliés ?
main.rb: Exemple conceptuel
# The Creator class declares the factory method that is supposed to return an
# object of a Product class. The Creator's subclasses usually provide the
# implementation of this method.
class Creator
# Note that the Creator may also provide some default implementation of the
# factory method.
def factory_method
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# Also note that, despite its name, the Creator's primary responsibility is
# not creating products. Usually, it contains some core business logic that
# relies on Product objects, returned by the factory method. Subclasses can
# indirectly change that business logic by overriding the factory method and
# returning a different type of product from it.
def some_operation
# Call the factory method to create a Product object.
product = factory_method
# Now, use the product.
"Creator: The same creator's code has just worked with #{product.operation}"
end
end
# Concrete Creators override the factory method in order to change the resulting
# product's type.
class ConcreteCreator1 < Creator
# Note that the signature of the method still uses the abstract product type,
# even though the concrete product is actually returned from the method. This
# way the Creator can stay independent of concrete product classes.
def factory_method
ConcreteProduct1.new
end
end
class ConcreteCreator2 < Creator
# @return [ConcreteProduct2]
def factory_method
ConcreteProduct2.new
end
end
# The Product interface declares the operations that all concrete products must
# implement.
class Product
# return [String]
def operation
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Products provide various implementations of the Product interface.
class ConcreteProduct1 < Product
# @return [String]
def operation
'{Result of the ConcreteProduct1}'
end
end
class ConcreteProduct2 < Product
# @return [String]
def operation
'{Result of the ConcreteProduct2}'
end
end
# The client code works with an instance of a concrete creator, albeit through
# its base interface. As long as the client keeps working with the creator via
# the base interface, you can pass it any creator's subclass.
def client_code(creator)
print "Client: I'm not aware of the creator's class, but it still works.\n"\
"#{creator.some_operation}"
end
puts 'App: Launched with the ConcreteCreator1.'
client_code(ConcreteCreator1.new)
puts "\n\n"
puts 'App: Launched with the ConcreteCreator2.'
client_code(ConcreteCreator2.new)
output.txt: Résultat de l’exécution
App: Launched with the ConcreteCreator1.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct1}
App: Launched with the ConcreteCreator2.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct2}
