Python 建造者模式

Builder Pattern是一种独特的设计模式，该模式有助于使用简单对象构建复杂对象并使用算法方法。该设计模式属于创作模式类别。在此设计模式中，构建器类按逐步过程构建最终对象。此构建器独立于其他对象。

1. 建造者模式的优点

• 它在类创建的指定对象的构造和表示之间提供了清晰的分隔和唯一的层。
• 它可以更好地控制所创建模式的构建过程。
• 它提供了更改对象内部表示的完美方案。

2. 如何实现建造者模式？

在本节中，我们将学习如何实现构建器模式。

# Filename : example.py
# Date : 2020-08-22
class Director:
    __builder = None
    def setBuilder(self, builder):
        self.__builder = builder
    def getCar(self):
        car = Car()
        # First goes the body
        body = self.__builder.getBody()
        car.setBody(body)
        # Then engine
        engine = self.__builder.getEngine()
        car.setEngine(engine)
        # and four wheels
        i = 0
        while i < 4:
            wheel = self.__builder.getWheel()
            car.attachWheel(wheel)
            i += 1
        return car
# The whole product
class Car:
    def __init__(self):
        self.__wheels = list()
        self.__engine = None
        self.__body = None
    def setBody(self, body):
        self.__body = body
    def attachWheel(self, wheel):
        self.__wheels.append(wheel)
    def setEngine(self, engine):
        self.__engine = engine
    def specification(self):
        print("body: %s" % self.__body.shape)
        print("engine horsepower: %d" % self.__engine.horsepower)
        print("tire size: %d" % self.__wheels[0].size)
class Builder:
    def getWheel(self): pass
    def getEngine(self): pass
    def getBody(self): pass
class JeepBuilder(Builder):
    def getWheel(self):
        wheel = Wheel()
        wheel.size = 22
        return wheel
    def getEngine(self):
        engine = Engine()
        engine.horsepower = 400
        return engine
    def getBody(self):
        body = Body()
        body.shape = "SUV"
        return body
# Car parts
class Wheel:
    size = None
class Engine:
    horsepower = None
class Body:
    shape = None
def main():
    jeepBuilder = JeepBuilder()
    director = Director()
    # Build Jeep
    print("Jeep")
    director.setBuilder(jeepBuilder)
    jeep = director.getCar()
    jeep.specification()
    print("")
if __name__ == "__main__":
    main()

输出

上面的程序生成以下输出-

Jeep
body: SUV
engine horsepower: 400
tire size: 22