Python 代码：
# Visitor Pattern with Python Code from abc import abstractmethod,ABCMeta # 定义一个表示元素（Element）的接口 class ComputerPart(metaclass=ABCMeta): @abstractmethod def accept(self, inComputerPartVisitor): pass #创建阔爱站了ComputerPart的实体类 class Keyboard(ComputerPart): def accept(self, inComputerPartVisitor): inComputerPartVisitor.visitKeyboard(self) class Monitor(ComputerPart): def accept(self, inComputerPartVisitor): inComputerPartVisitor.visitMonitor(self) class Mouse(ComputerPart): def accept(self, inComputerPartVisitor): inComputerPartVisitor.visitMouse(self) class Computer(ComputerPart): _parts = [] def __init__(self): self._parts.append(Mouse()) self._parts.append(Keyboard()) self._parts.append(Monitor()) def accept(self, inComputerPartVisitor): for aPart in self._parts : aPart.accept(inComputerPartVisitor) inComputerPartVisitor.visitComputer(self) # 定义一个表示访问者的接口 class ComputerPartVisitor(metaclass=ABCMeta): @abstractmethod def visitComputer(self,inComputer): pass @abstractmethod def visitMouse(self,inMouse): pass @abstractmethod def visitKeyboard(self,inKeyboard): pass @abstractmethod def visitMonitor(self,inMonitor): pass # 实现访问者接口的实体类 class ComputerPartDisplayVisitor(ComputerPartVisitor): def visitComputer(self,inComputer): print("Displaying {0}. Called in {1}".format(inComputer.__class__.__name__,self.__class__.__name__)) def visitMouse(self,inMouse): print("Displaying {0}. Called in {1}".format(inMouse.__class__.__name__,self.__class__.__name__)) def visitKeyboard(self,inKeyboard): print("Displaying {0}. Called in {1}".format(inKeyboard.__class__.__name__,self.__class__.__name__)) def visitMonitor(self,inMonitor): print("Displaying {0}. Called in {1}".format(inMonitor.__class__.__name__,self.__class__.__name__)) # 调用输出 if __name__ == '__main__': aComputer = Computer() aComputer.accept(ComputerPartDisplayVisitor())
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