中介者是一种行为设计模式， 让程序组件通过特殊的中介者对象进行间接沟通， 达到减少组件之间依赖关系的目的。
中介者能使得程序更易于修改和扩展， 而且能更方便地对独立的组件进行复用， 因为它们不再依赖于很多其他的类。
使用示例： 中介者模式在 Python 代码中最常用于帮助程序 GUI 组件之间的通信。 在 MVC 模式中， 控制器是中介者的同义词。
from__future__importannotationsfromabcimportABCclassMediator(ABC):""" The Mediator interface declares a method used by components to notify the mediator about various events. The Mediator may react to these events and pass the execution to other components. """defnotify(self,sender:object,event:str)->None:passclassConcreteMediator(Mediator):def__init__(self,component1:Component1,component2:Component2)->None:self._component1=component1 self._component1.mediator=self self._component2=component2 self._component2.mediator=selfdefnotify(self,sender:object,event:str)->None:ifevent=="A":print("Mediator reacts on A and triggers following operations:")self._component2.do_c()elifevent=="D":print("Mediator reacts on D and triggers following operations:")self._component1.do_b()self._component2.do_c()classBaseComponent:""" The Base Component provides the basic functionality of storing a mediator's instance inside component objects. """def__init__(self,mediator:Mediator=None)->None:self._mediator=mediator@propertydefmediator(self)->Mediator:returnself._mediator@mediator.setterdefmediator(self,mediator:Mediator)->None:self._mediator=mediator""" Concrete Components implement various functionality. They don't depend on other components. They also don't depend on any concrete mediator classes. """classComponent1(BaseComponent):defdo_a(self)->None:print("Component 1 does A.")self.mediator.notify(self,"A")defdo_b(self)->None:print("Component 1 does B.")self.mediator.notify(self,"B")classComponent2(BaseComponent):defdo_c(self)->None:print("Component 2 does C.")self.mediator.notify(self,"C")defdo_d(self)->None:print("Component 2 does D.")self.mediator.notify(self,"D")if__name__=="__main__":# The client code.c1=Component1()c2=Component2()mediator=ConcreteMediator(c1,c2)print("Client triggers operation A.")c1.do_a()print("\n",end="")print("Client triggers operation D.")c2.do_d()输出：
Client triggers operation A. Component 1 does A. Mediator reacts on A and triggers following operations: Component 2 does C. Client triggers operation D. Component 2 does D. Mediator reacts on D and triggers following operations: Component 1 does B. Component 2 does C.可以看出是让中介去写触发之后的逻辑链条。
