Question

我正在尝试使用pytransitions版本0.6.4的内部转换功能，但它对我不起作用。我收到错误

  File "/python3.6/site-packages/transitions/core.py", line 720, in set_state
mod.state = state.name
AttributeError: 'NoneType' object has no attribute 'name'

我在这里调整了代码

mod.state = state.name if state else mod.state

然后它在其他地方出错了，所以我不确定这个功能是否有问题。

我正在用一个dicts列表初始化机器，因为它的转换是kwarg。一个dict的例子是，我相信这是正确的格式。

{'trigger': 'cartridge_present_switch', 'source': 'post', 'dest': None, 'before': 'on_cartridge_present_switch'}

虽然文档仅显示使用add_transition方法添加的转换，如下所示

machine.add_transition('internal', ['liquid', 'gas'], None, after='change_shape')

有人可以对内部过渡功能发表评论吗？

谢谢，约翰

Answer 1

在0.6.6中引入了内部转场，如Changelog所示。传递给构造函数的转换也将使用add_transition(s)进行处理。更准确地说，分配给构造函数的关键字transitions的值只是“按原样”传递给add_transitions，其中参数被解包，并且每个过渡单独调用add_transition。当然，这个过程不是防弹的。然而，如果您遇到add_transition有效但通过构造函数传递的问题，我建议您再次检查参数列表。

from transitions import Machine

class Model():

    def model_callback(self):
        print("callback called")
        pass


states = ['A', 'B']
transitions = [{'trigger': 'internal', 'source': 'A', 
                'dest': None, 'after': 'model_callback'}]

# variant 1, passing transitions via constructor
model = Model()
m = Machine(model, states=['A', 'B'], transitions=transitions, initial='A')
model.internal()  # >>> callback called

# variant 2, passing transitions to `add_transitions` for batch processing
model = Model()
m = Machine(model, states=['A', 'B'], initial='A')
m.add_transitions(transitions)
model.internal()  # >>> callback called

# variant 3, passing transitions individually to `add_transition`
model = Model()
m = Machine(model, states=['A', 'B'], initial='A')
# accessing an element of transition list and map the keywords
# to the method parameters; basically what `add_transitions` is doing
m.add_transition(**transitions[0])
model.internal()  # >>> callback called

pytransitions的内部转换是否有效

1 个答案: