Factory Method en Python
Factory method es un patrón de diseño creacional que resuelve el problema de crear objetos de producto sin especificar sus clases concretas.
El patrón Factory Method define un método que debe utilizarse para crear objetos, en lugar de una llamada directa al constructor (operador new). Las subclases pueden sobrescribir este método para cambiar las clases de los objetos que se crearán.
Si no sabes la diferencia entre varios patrones y conceptos de la fábrica, lee nuestra Comparación de fábricas.
Complejidad:
Popularidad:
Ejemplos de uso: El patrón Factory Method se utiliza mucho en el código Python. Resulta muy útil cuando necesitas proporcionar un alto nivel de flexibilidad a tu código.
Identificación: Los métodos fábrica pueden ser reconocidos por métodos de creación, que crean objetos de clases concretas, pero los devuelven como objetos del tipo abstracto o interfaz.
Ejemplo conceptual
Este ejemplo ilustra la estructura del patrón de diseño Factory Method. Se centra en responder las siguientes preguntas:
- ¿De qué clases se compone?
- ¿Qué papeles juegan esas clases?
- ¿De qué forma se relacionan los elementos del patrón?
main.py: Ejemplo conceptual
from __future__ import annotations
from abc import ABC, abstractmethod
class Creator(ABC):
"""
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.
"""
@abstractmethod
def factory_method(self):
"""
Note that the Creator may also provide some default implementation of
the factory method.
"""
pass
def some_operation(self) -> str:
"""
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.
"""
# Call the factory method to create a Product object.
product = self.factory_method()
# Now, use the product.
result = f"Creator: The same creator's code has just worked with {product.operation()}"
return result
"""
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(self) -> Product:
return ConcreteProduct1()
class ConcreteCreator2(Creator):
def factory_method(self) -> Product:
return ConcreteProduct2()
class Product(ABC):
"""
The Product interface declares the operations that all concrete products
must implement.
"""
@abstractmethod
def operation(self) -> str:
pass
"""
Concrete Products provide various implementations of the Product interface.
"""
class ConcreteProduct1(Product):
def operation(self) -> str:
return "{Result of the ConcreteProduct1}"
class ConcreteProduct2(Product):
def operation(self) -> str:
return "{Result of the ConcreteProduct2}"
def client_code(creator: Creator) -> None:
"""
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.
"""
print(f"Client: I'm not aware of the creator's class, but it still works.\n"
f"{creator.some_operation()}", end="")
if __name__ == "__main__":
print("App: Launched with the ConcreteCreator1.")
client_code(ConcreteCreator1())
print("\n")
print("App: Launched with the ConcreteCreator2.")
client_code(ConcreteCreator2())
Output.txt: Resultado de la ejecución
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}
