Question

为什么这段代码显然不能正常工作？

下面的机器有两种状态：idle和travelling，以及两个名为go的转换。我使用register_handlers附加到此转换on_enter和on_go处理程序。我希望这段代码的结果是两个打印，每个处理程序之一。出于某种原因，似乎只有on_enter处理程序被执行。

import pysm

machine = pysm.pysm.StateMachine('ship')

idle = pysm.pysm.State('idle')

class TravellingState(pysm.pysm.State):
    def on_go(self, state, event):
        print("on_go function called")

    def on_enter(self, state, event):
        print("on_enter function called")

    def register_handlers(self):
        self.handlers = {
            'enter': self.on_enter,
            'go': self.on_go, # doesnt work?
        }

travelling = TravellingState('travelling')

machine.add_state(idle, initial=True)
machine.add_state(travelling)

machine.add_transition(from_state=idle, to_state=travelling, events=['go'])

machine.initialize()

machine.dispatch(pysm.pysm.Event('go', cargo={'target':(1,1)}))

Answer 1

go是travelling州将处理的事件。但是你最初处于idle状态。它会忽略go事件。

您已在idle事件中创建了从travelling到go的转换。因此，您基本上看到的是从idle到travelling的转换，因此调用enter实例中的Travelling处理程序。

如果要在go状态下处理idle，请在idle实例中指定处理程序：

def on_go(state, event):
    print('on_go from idle')

idle = pysm.pysm.State('idle')
idle.handlers = {'go': on_go}

然后致电

machine.dispatch(pysm.pysm.Event('go', cargo={'target':(1,1)}))

调用on_go状态的idle处理程序。

同时

保留您的代码，如果您再次调用go事件（已处于travelling状态），则会调用您的处理程序。

machine.dispatch(pysm.pysm.Event('go', cargo={'target':(1,1)}))

完整的工作示例：

import pysm machine = pysm.pysm.StateMachine('ship') def on_go(state, event): print('on_go from idle') idle = pysm.pysm.State('idle') idle.handlers = {'go': on_go} class TravellingState(pysm.pysm.State): def on_go(self, state, event): print("on_go from travelling") def on_enter(self, state, event): print("on_enter from travelling") def register_handlers(self): self.handlers = { 'enter': self.on_enter, 'go': self.on_go, } travelling = TravellingState('travelling') machine.add_state(idle, initial=True) machine.add_state(travelling) machine.add_transition(from_state=idle, to_state=travelling, events=['go']) machine.initialize() machine.dispatch(pysm.pysm.Event('go', cargo={'target':(1,1)})) machine.dispatch(pysm.pysm.Event('go', cargo={'target':(1,1)}))

正如预期的那样输出：

# go event is dispatched on_go from idle # Now the transition happens on_enter from travelling # go is dispatched again on_go from travelling

带有模块`pysm`的Python有限状态机

1 个答案: