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Facade en Python
Facade es un patrón de diseño estructural que proporciona una interfaz simplificada (pero limitada) a un sistema complejo de clases, bibliotecas o _frameworks_.
El patrón Facade disminuye la complejidad general de la aplicación, al mismo tiempo que ayuda a mover dependencias no deseadas a un solo lugar.
Complejidad:
Popularidad:
Ejemplos de uso: El patrón Facade se utiliza habitualmente en aplicaciones escritas en Python. Es de especial utilidad al trabajar con bibliotecas y API complejas.
Identificación: El patrón Facade se puede reconocer en una clase con una interfaz simple, pero que delega la mayor parte del trabajo a otras clases. Normalmente, las fachadas gestionan todo el ciclo de vida de los objetos que utilizan.
Ejemplo conceptual
Este ejemplo ilustra la estructura del patrón de diseño Facade. 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
class Facade:
"""
The Facade class provides a simple interface to the complex logic of one or
several subsystems. The Facade delegates the client requests to the
appropriate objects within the subsystem. The Facade is also responsible for
managing their lifecycle. All of this shields the client from the undesired
complexity of the subsystem.
"""
def __init__(self, subsystem1: Subsystem1, subsystem2: Subsystem2) -> None:
"""
Depending on your application's needs, you can provide the Facade with
existing subsystem objects or force the Facade to create them on its
own.
"""
self._subsystem1 = subsystem1 or Subsystem1()
self._subsystem2 = subsystem2 or Subsystem2()
def operation(self) -> str:
"""
The Facade's methods are convenient shortcuts to the sophisticated
functionality of the subsystems. However, clients get only to a fraction
of a subsystem's capabilities.
"""
results = []
results.append("Facade initializes subsystems:")
results.append(self._subsystem1.operation1())
results.append(self._subsystem2.operation1())
results.append("Facade orders subsystems to perform the action:")
results.append(self._subsystem1.operation_n())
results.append(self._subsystem2.operation_z())
return "\n".join(results)
class Subsystem1:
"""
The Subsystem can accept requests either from the facade or client directly.
In any case, to the Subsystem, the Facade is yet another client, and it's
not a part of the Subsystem.
"""
def operation1(self) -> str:
return "Subsystem1: Ready!"
# ...
def operation_n(self) -> str:
return "Subsystem1: Go!"
class Subsystem2:
"""
Some facades can work with multiple subsystems at the same time.
"""
def operation1(self) -> str:
return "Subsystem2: Get ready!"
# ...
def operation_z(self) -> str:
return "Subsystem2: Fire!"
def client_code(facade: Facade) -> None:
"""
The client code works with complex subsystems through a simple interface
provided by the Facade. When a facade manages the lifecycle of the
subsystem, the client might not even know about the existence of the
subsystem. This approach lets you keep the complexity under control.
"""
print(facade.operation(), end="")
if __name__ == "__main__":
# The client code may have some of the subsystem's objects already created.
# In this case, it might be worthwhile to initialize the Facade with these
# objects instead of letting the Facade create new instances.
subsystem1 = Subsystem1()
subsystem2 = Subsystem2()
facade = Facade(subsystem1, subsystem2)
client_code(facade)
Output.txt: Resultado de la ejecución
Facade initializes subsystems:
Subsystem1: Ready!
Subsystem2: Get ready!
Facade orders subsystems to perform the action:
Subsystem1: Go!
Subsystem2: Fire!
