Python: State Pattern

GeovinDuState.py

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#状态模式 State  Pattern class ComputerState(object):     name = "state"     allowed = []       def switch(self, state):         """ Switch to new state """         if state.name in self.allowed:             print(             '当前对象:', self, ' => 切换到新状态', state.name)             self.__class__ = state         else:             print(             '当前对象:', self, ' => 切换到 ', state.name, '不可能的.')           def __str__(self):            return self.name   # ComputerState class Off(ComputerState):      name = "off"    allowed = ['on']   # ComputerState class On(ComputerState):     """ State of being powered on and working """     name = "on"     allowed = ['off', 'suspend', 'hibernate']   # ComputerState class Suspend(ComputerState):     """ State of being in suspended mode after switched on """     name = "suspend"     allowed = ['on']   # ComputerState class Hibernate(ComputerState):     """ State of being in hibernation after powered on """     name = "hibernate"     allowed = ['on']     class Computer(object):     """ A class representing a computer """       def __init__(self, model='HP'):         self.model = model         # State of the computer - default is off.         self.state = Off()       def change(self, state):         """ Change state """         self.state.switch(state)     """2 State class: Base State class"""     class DuState:     """Base state. This is to share functionality"""       def scan(self):         """Scan the dial to the next station"""         self.pos += 1           """check for the last station"""         if self.pos == len(self.stations):             self.pos = 0         print("参观... 站点是 {} {}".format(self.stations[self.pos], self.name))     """Separate Class for AM state of the radio"""     class AmState(DuState):     """constructor for AM state class"""       def __init__(self, radio):         self.radio = radio         self.stations = ["1250", "1380", "1510"]         self.pos = 0         self.name = "AM"       """method for toggling the state"""       def toggle_amfm(self):         print("切换到 FM")         self.radio.state = self.radio.fmstate     """Separate class for FM state"""     class FmState(DuState):     """Constriuctor for FM state"""       def __init__(self, radio):         self.radio = radio         self.stations = ["81.3", "89.1", "103.9"]         self.pos = 0         self.name = "FM"       """method for toggling the state"""       def toggle_amfm(self):         print("切换到 AM")         self.radio.state = self.radio.amstate     """Dedicated class Radio"""     class Radio:     """A radio. It has a scan button, and an AM / FM toggle switch."""       def __init__(self):         """We have an AM state and an FM state"""         self.fmstate = FmState(self)         self.amstate = AmState(self)         self.state = self.fmstate       """method to toggle the switch"""       def toggle_amfm(self):         self.state.toggle_amfm()       """method to scan """       def scan(self):         self.state.scan()   # Geovin Du 3 class Context:     _state = None     """ A reference to the current state."""       def __init__(self, state):         self.transition_to(state)       def transition_to(self, state):         """Method to make transition"""           print(f"Context: Transition to {type(state).__name__}")         self._state = state         self._state.context = self       def request1(self):         self._state.handle1()       def request2(self):         self._state.handle2()     class GeovinState:     """An abstract class for Concrete sub-classes"""       @property     def context(self):         return self._context       @context.setter     def context(self, context: Context):         self._context = context       # @abstractmethod     def handle1(self):         pass       # @abstractmethod     def handle2(self):         pass   class State_A(GeovinState):     def handle1(self):         print("State_A handles request1.")         print("State_A wants to change the state of the context.")         self.context.transition_to(State_B())       def handle2(self):         print("State_A handles request2.")   class State_B(GeovinState):     def handle1(self):         print("State_B handles request1.")       def handle2(self):         print("State_B handles request2.")         print("State_B wants to change the state of the context.")         self.context.transition_to(State_A())

　　

 

main.py 调用：

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# 状态模式 State  Pattern comp = GeovinDuState.Computer() comp.change(GeovinDuState.On) comp.change(GeovinDuState.Off) comp.change(GeovinDuState.On) comp.change(GeovinDuState.Suspend) comp.change(GeovinDuState.Hibernate) comp.change(GeovinDuState.On) comp.change(GeovinDuState.Off)   radio = GeovinDuState.Radio() actions = [radio.scan] * 3 + [radio.toggle_amfm] + [radio.scan] * 3 actions *= 2   for action in actions:      action()   context = GeovinDuState.Context(GeovinDuState.State_A()) context.request1() context.request2()

　　

输出

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当前对象: <GeovinDuState.Off object at 0x000001F25CA44CD0>  => 切换到新状态 on 当前对象: <GeovinDuState.On object at 0x000001F25CA44CD0>  => 切换到新状态 off 当前对象: <GeovinDuState.Off object at 0x000001F25CA44CD0>  => 切换到新状态 on 当前对象: <GeovinDuState.On object at 0x000001F25CA44CD0>  => 切换到新状态 suspend 当前对象: <GeovinDuState.Suspend object at 0x000001F25CA44CD0>  => 切换到  hibernate 不可能的. 当前对象: <GeovinDuState.Suspend object at 0x000001F25CA44CD0>  => 切换到新状态 on 当前对象: <GeovinDuState.On object at 0x000001F25CA44CD0>  => 切换到新状态 off 参观... 站点是 89.1 FM 参观... 站点是 103.9 FM 参观... 站点是 81.3 FM 切换到 AM 参观... 站点是 1380 AM 参观... 站点是 1510 AM 参观... 站点是 1250 AM 参观... 站点是 1380 AM 参观... 站点是 1510 AM 参观... 站点是 1250 AM 切换到 FM 参观... 站点是 89.1 FM 参观... 站点是 103.9 FM 参观... 站点是 81.3 FM Context: Transition to State_A State_A handles request1. State_A wants to change the state of the context. Context: Transition to State_B State_B handles request2. State_B wants to change the state of the context. Context: Transition to State_A