Python 設計模式 - 構建器

構建器模式是一種獨特的設計模式，它使用簡單的物件構建複雜的物件，並採用演算法方法。此設計模式屬於建立模式範疇。在此設計模式中，構建器類分步構建最終物件。此構建器獨立於其他物件。

構建器模式的優勢

• 它在類建立的指定物件的構建和表示之間提供了明確的分離和一個獨特的層。

• 它對建立的模式的構建過程提供了更好的控制。

• 它提供了改變物件內部表示的完美場景。

如何實現構建器模式？

在本節中，我們將學習如何實現構建器模式。

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()

輸出

上述程式生成以下輸出 −