时间戳

首页 > 解决方案 > Pytransitions 中的嵌套

python - Pytransitions 中的嵌套

问题描述

我一直在 github、SO 和谷歌搜索上查看已解决的问题以解决此问题。但我无法解决我的问题，这似乎是正确的地方。我已经在 github 上打开了一个问题，但我不确定这是否是正确的做法。我正在制作一个可以包含多个子状态的状态机，这些子状态也是所有状态机。因此，这基本上归结为根据自述文件重用 HSM 。

我最高级别的 SM 是这样的：

from transitions.extensions import LockedHierarchicalMachine as Machine
from coordination.running import RunningStateMachine

logging.basicConfig(level=logging.ERROR)
logging.getLogger("transitions").setLevel(logging.INFO)

class RPPStateMachine(Machine):
    def __init__(self, name):
        self._running = RunningStateMachine()
        self.name = name
        states = [
            "init",
            {"name": "running", "children": self._running},
            "stop",
        ]

        Machine.__init__(self, states=states, initial="init")

        self.add_transition("e_run", "init", "run", after=self.run_machine)
        self.add_transition("e_stop", "*", "stop")

    def run_machine(self):
        self._running.initialize()

如您所见，状态机具有三个状态init，running和stop。一旦e_run()通过类似的方式发送事件

machine = RPPStateMachine("my_machine")
machine.e_run()

机器转换到running状态。

我以间接的方式这样做，因为我希望事情自动发生。e_run()导致转换running并随后run_machine调用initialize运行类的方法，该方法触发一个事件以启动事件链。下面我展示running了这一切。

所以运行状态定义为

from transitions.extensions import LockedHierarchicalMachine as Machine
from coordination.test_mode import TestingStateMachine
from coordination.release_mode import ReleaseStateMachine

class RunningStateMachine(Machine):
    def __init__(self):
        self._test_mode = TestingStateMachine()
        self._release_demo = ReleaseStateMachine()
        states = [
            "init",
            "configuration",
            "idle",
            {"name": "test_mode", "children": self._test_mode},
            {"name": "release_mode", "children": self._release_mode},
        ]

        Machine.__init__(self, states=states, initial="init")
        self.add_transition("e_start_running", "init", "configuration", after=self.configuration)
        self.add_transition("e_success_config", "configuration", "idle")
        self.add_transition("e_test_mode", "idle", "test_mode")
        self.add_transition("e_release_mode", "idle", "release_mode")
        self.add_transition("e_start_running", "idle", "init")

    def initialize(self):
        print("Initialization step for running, emitting e_start.")
        self.e_start_running()

    def configuration(self):
        print("Configuring...")
        print( "Current state: " + self.state)

        self.e_success_config()

它类似于它的父状态，由几个状态和几个子状态组成。我还启用了日志记录以查看我进入和退出的状态。根据我的经验，嵌套状态机非常有用，因为您可以重用之前编写的状态。此外，随着您的状态机的增长，它有助于使事情更加模块化。因此，任何状态都不会变得庞大且难以阅读/理解。

所以不寻常的行为是，当e_run()被调用时，我得到了

INFO:transitions.core:Entered state running
INFO:transitions.core:Entered state running_init
Initialization step for running, emitting e_start.
INFO:transitions.core:Exited state init
INFO:transitions.core:Entered state configuration
Configuring...
current state: configuration
INFO:transitions.core:Exited state configuration
INFO:transitions.core:Entered state idle

如你所见

machine.state
>>> 'running_init'

尽管

machine._running.state
>>> 'idle'

我当然可以将转换定义移动到父状态，但这并不方便。我不能对所有子州都这样做。显然，我希望每个子状态对自己的行为负责。这里的常见做法是什么？这是错误还是预期行为？

如何将状态机整齐地嵌套在彼此之下？

标签： pythontransitionfsmpytransitions

解决方案

从transitions0.7.1 开始，将状态机作为另一个状态机的子级传递会将传递的机器的所有状态复制到父级。传递的状态机保持不变（正如我们在此处讨论的那样）。

from transitions.extensions import MachineFactory

HSM = MachineFactory.get_predefined(nested=True)

fsm = HSM(states=['A', 'B'], initial='A')
hsm = HSM(states=['1', {'name': '2', 'children': fsm}])

# states object have been copied instead of referenced, they are not identical
assert fsm.states['A'] is not hsm.states['2_A']
hsm.to_2_A()

# both machines work with different models
assert fsm.models[0] is not hsm.models[0]
assert fsm.state is not hsm.state

当前推荐的工作流程是拆分模型和机器，并将机器仅视为其父级的某种“蓝图”：

from transitions.extensions import MachineFactory


class Model:
    pass


HSM = MachineFactory.get_predefined(nested=True)

# creating fsm as a blueprint, it does not need a model
fsm = HSM(model=None, states=['A', 'B'], initial='A')
# use a model AND also
model = Model()
hsm = HSM(model=['self', model], states=['1', {'name': '2', 'children': fsm}])

# will only update the machine's state
hsm.to_1()
assert model.state != hsm.state
# will update ALL model states
hsm.dispatch("to_2_B")
assert model.state == hsm.state

但是，这并不能取代将机器正确隔离（和/或范围）嵌套到父机器中。已经创建了一个功能草案，并有望在可预见的将来实现。

推荐阅读