生成器模式

from __future__ import annotations
from abc import ABC, abstractmethod, abstractproperty
from typing import Any


class Builder(ABC):
    """
    The Builder interface specifies methods for creating the different parts of
    the Product objects.
    """

    @abstractproperty
    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()

Standard basic product:
Product parts: PartA1

Standard full featured product:
Product parts: PartA1, PartB1, PartC1

Custom product:
Product parts: PartA1, PartB1

// 只有当产品较为复杂且需要详细配置时，使用生成器模式才有意义。下面的两个
// 产品尽管没有同样的接口，但却相互关联。
class Car is
    // 一辆汽车可能配备有 GPS 设备、行车电脑和几个座位。不同型号的汽车（
    // 运动型轿车、SUV 和敞篷车）可能会安装或启用不同的功能。

class Manual is
    // 用户使用手册应该根据汽车配置进行编制，并介绍汽车的所有功能。


// 生成器接口声明了创建产品对象不同部件的方法。
interface Builder is
    method reset()
    method setSeats(...)
    method setEngine(...)
    method setTripComputer(...)
    method setGPS(...)

// 具体生成器类将遵循生成器接口并提供生成步骤的具体实现。你的程序中可能会
// 有多个以不同方式实现的生成器变体。
class CarBuilder implements Builder is
    private field car:Car

    // 一个新的生成器实例必须包含一个在后续组装过程中使用的空产品对象。
    constructor CarBuilder() is
        this.reset()

    // reset（重置）方法可清除正在生成的对象。
    method reset() is
        this.car = new Car()

    // 所有生成步骤都会与同一个产品实例进行交互。
    method setSeats(...) is
        // 设置汽车座位的数量。

    method setEngine(...) is
        // 安装指定的引擎。

    method setTripComputer(...) is
        // 安装行车电脑。

    method setGPS(...) is
        // 安装全球定位系统。

    // 具体生成器需要自行提供获取结果的方法。这是因为不同类型的生成器可能
    // 会创建不遵循相同接口的、完全不同的产品。所以也就无法在生成器接口中
    // 声明这些方法（至少在静态类型的编程语言中是这样的）。
    //
    // 通常在生成器实例将结果返回给客户端后，它们应该做好生成另一个产品的
    // 准备。因此生成器实例通常会在 `getProduct（获取产品）`方法主体末尾
    // 调用重置方法。但是该行为并不是必需的，你也可让生成器等待客户端明确
    // 调用重置方法后再去处理之前的结果。
    method getProduct():Car is
        product = this.car
        this.reset()
        return product

// 生成器与其他创建型模式的不同之处在于：它让你能创建不遵循相同接口的产品。
class CarManualBuilder implements Builder is
    private field manual:Manual

    constructor CarManualBuilder() is
        this.reset()

    method reset() is
        this.manual = new Manual()

    method setSeats(...) is
        // 添加关于汽车座椅功能的文档。

    method setEngine(...) is
        // 添加关于引擎的介绍。

    method setTripComputer(...) is
        // 添加关于行车电脑的介绍。

    method setGPS(...) is
        // 添加关于 GPS 的介绍。

    method getProduct():Manual is
        // 返回使用手册并重置生成器。


// 主管只负责按照特定顺序执行生成步骤。其在根据特定步骤或配置来生成产品时
// 会很有帮助。由于客户端可以直接控制生成器，所以严格意义上来说，主管类并
// 不是必需的。
class Director is
    private field builder:Builder

    // 主管可同由客户端代码传递给自身的任何生成器实例进行交互。客户端可通
    // 过这种方式改变最新组装完毕的产品的最终类型。
    method setBuilder(builder:Builder)
        this.builder = builder

    // 主管可使用同样的生成步骤创建多个产品变体。
    method constructSportsCar(builder: Builder) is
        builder.reset()
        builder.setSeats(2)
        builder.setEngine(new SportEngine())
        builder.setTripComputer(true)
        builder.setGPS(true)

    method constructSUV(builder: Builder) is
        // ...


// 客户端代码会创建生成器对象并将其传递给主管，然后执行构造过程。最终结果
// 将需要从生成器对象中获取。
class Application is

    method makeCar() is
        director = new Director()

        CarBuilder builder = new CarBuilder()
        director.constructSportsCar(builder)
        Car car = builder.getProduct()

        CarManualBuilder builder = new CarManualBuilder()
        director.constructSportsCar(builder)

        // 最终产品通常需要从生成器对象中获取，因为主管不知晓具体生成器和
        // 产品的存在，也不会对其产生依赖。
        Manual manual = builder.getProduct()