Python 设计模式 - 建造者模式(Builder Pattern)

建造者模式(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建模式的范畴。 在这种设计模式中，构建器类逐步构建最终对象。 此构建器独立于其他对象。

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。

• 它提供了更改对象内部表示的完美方案。

Python 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。

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

以上程序生成如下输出 −