Python 设计模式 - 生成器模式

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  简述

  Builder Pattern 是一种独特的设计模式，它有助于使用简单的对象构建复杂的对象并使用算法方法。这种设计模式属于创造模式的范畴。在此设计模式中，构建器类逐步构建最终对象。此构建器独立于其他对象。

  生成器模式的优点

  • 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离和独特的层。
  • 它可以更好地控制所创建模式的构建过程。
  • 它为更改对象的内部表示提供了完美的场景。
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  如何实现生成器模式？

  在本节中，我们将学习如何实现构建器模式。

  
  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() # initializing the class
     
     director = Director()
     
     # Build Jeep
     print "Jeep"
     director.setBuilder(jeepBuilder)
     jeep = director.getCar()
     jeep.specification()
     print ""
  if __name__ == "__main__":
     main()
  

  输出

  上述程序生成以下输出 -