Le Monteur est un patron de conception de création qui permet de construire des objets complexes étape par étape.
Le monteur n’est pas comme les autres patrons de création : les produits n’ont pas besoin d’avoir une interface commune. Il est ainsi possible de créer différents produits en utilisant le même procédé de fabrication.
Complexité :
Popularité :
Exemples d’utilisation : Le monteur est bien connu dans le monde du Python. Il se montre très utile lorsque vous devez créer un objet possédant de nombreuses configurations possibles.
Identification : Le monteur peut être identifié à l’intérieur d’une classe qui n’a qu’une seule méthode de création et plusieurs méthodes permettant de configurer l’objet en résultant. Les méthodes du monteur prennent souvent en charge le chaînage (par exemple, someBuilder.setValueA(1).setValueB(2).create()
).
Exemple conceptuel
Dans cet exemple, nous allons voir la structure du patron de conception Monteur . Nous allons répondre aux questions suivantes :
Que contiennent les classes ?
Quels rôles jouent-elles ?
Comment les éléments du patron sont-ils reliés ?
main.py: Exemple conceptuel
from __future__ import annotations
from abc import ABC, abstractmethod
from typing import Any
class Builder(ABC):
"""
The Builder interface specifies methods for creating the different parts of
the Product objects.
"""
@property
@abstractmethod
def product(self) -> None:
pass
@abstractmethod
def produce_part_a(self) -> None:
pass
@abstractmethod
def produce_part_b(self) -> None:
pass
@abstractmethod
def produce_part_c(self) -> None:
pass
class ConcreteBuilder1(Builder):
"""
The Concrete Builder classes follow the Builder interface and provide
specific implementations of the building steps. Your program may have
several variations of Builders, implemented differently.
"""
def __init__(self) -> None:
"""
A fresh builder instance should contain a blank product object, which is
used in further assembly.
"""
self.reset()
def reset(self) -> None:
self._product = Product1()
@property
def product(self) -> Product1:
"""
Concrete Builders are supposed to provide their own methods for
retrieving results. That's because various types of builders may create
entirely different products that don't follow the same interface.
Therefore, such methods cannot be declared in the base Builder interface
(at least in a statically typed programming language).
Usually, after returning the end result to the client, a builder
instance is expected to be ready to start producing another product.
That's why it's a usual practice to call the reset method at the end of
the `getProduct` method body. However, this behavior is not mandatory,
and you can make your builders wait for an explicit reset call from the
client code before disposing of the previous result.
"""
product = self._product
self.reset()
return product
def produce_part_a(self) -> None:
self._product.add("PartA1")
def produce_part_b(self) -> None:
self._product.add("PartB1")
def produce_part_c(self) -> None:
self._product.add("PartC1")
class Product1():
"""
It makes sense to use the Builder pattern only when your products are quite
complex and require extensive configuration.
Unlike in other creational patterns, different concrete builders can produce
unrelated products. In other words, results of various builders may not
always follow the same interface.
"""
def __init__(self) -> None:
self.parts = []
def add(self, part: Any) -> None:
self.parts.append(part)
def list_parts(self) -> None:
print(f"Product parts: {', '.join(self.parts)}", end="")
class Director:
"""
The Director is only responsible for executing the building steps in a
particular sequence. It is helpful when producing products according to a
specific order or configuration. Strictly speaking, the Director class is
optional, since the client can control builders directly.
"""
def __init__(self) -> None:
self._builder = None
@property
def builder(self) -> Builder:
return self._builder
@builder.setter
def builder(self, builder: Builder) -> None:
"""
The Director works with any builder instance that the client code passes
to it. This way, the client code may alter the final type of the newly
assembled product.
"""
self._builder = builder
"""
The Director can construct several product variations using the same
building steps.
"""
def build_minimal_viable_product(self) -> None:
self.builder.produce_part_a()
def build_full_featured_product(self) -> None:
self.builder.produce_part_a()
self.builder.produce_part_b()
self.builder.produce_part_c()
if __name__ == "__main__":
"""
The client code creates a builder object, passes it to the director and then
initiates the construction process. The end result is retrieved from the
builder object.
"""
director = Director()
builder = ConcreteBuilder1()
director.builder = builder
print("Standard basic product: ")
director.build_minimal_viable_product()
builder.product.list_parts()
print("\n")
print("Standard full featured product: ")
director.build_full_featured_product()
builder.product.list_parts()
print("\n")
# Remember, the Builder pattern can be used without a Director class.
print("Custom product: ")
builder.produce_part_a()
builder.produce_part_b()
builder.product.list_parts()
Output.txt: Résultat de l’exécution
Standard basic product:
Product parts: PartA1
Standard full featured product:
Product parts: PartA1, PartB1, PartC1
Custom product:
Product parts: PartA1, PartB1