我正在尝试使用transitions模块实现状态机。 Python版本2.7.13和过渡版本是0.4.4版本。
在项目文档中，示例都通过在命令提示符下键入函数调用来进行状态。从转换文档中的第一个示例获取片段，wake_up的状态是通过调用命名函数work_out和>>> batman.wake_up()
>>> batman.work_out()
>>> batman.state
'hungry'
next_state我希望状态机能够自动前进通过模型数据的状态。下面的玩具示例是我想要做的但是依赖于使用虚拟函数作为设置next_state的指针。
有没有办法做到这一点，不涉及创建from transitions import Machine
class AModel(object):
def __init__(self):
self.sv = 0 # state variable of the model
def on_enter_sA(self):
print "Entered sA"
self.next_state = self.to_sB
def on_enter_sB(self):
print "Entered sB"
if self.sv < 3:
self.next_state = self.to_sB
else:
self.next_state = self.to_sC
def on_enter_sC(self):
print "Entered sC"
if self.sv == 6:
self.next_state = self.to_sD
def on_enter_sD(self):
print "Entered sD"
self.next_state = self.to_sA
def next_state(self):
pass
#setup model and state machine
model = AModel()
#init transitions model
list_of_states = ['sA','sB','sC','sD']
transitions = [
{'trigger':'to_sA','source':'sD','dest':'sA'},
{'trigger':'to_sB','source':'sA','dest':'sB'},
{'trigger':'to_sC','source':'sB','dest':'sC'},
{'trigger':'to_sD','source':'sC','dest':'sD'}
]
machine = Machine(model=model, states=list_of_states, initial='sA',
transitions=transitions)
model.next_state = model.to_sB #init next state pointer
#begin main
for i in range(0,8):
print 'iter is: ' + str(i) + " -model state is:" + model.state
model.sv = i #update model state variable, local state logic
#will determine what next_state points to
model.next_state()
函数并像指针一样使用它？转换文档具有Ordered转换和条件转换但我真正想要的是具有条件有序转换。
是否可以在不使用函数指针的情况下重写下面的代码？
{{1}}
谢谢！
答案 0 :(得分：2)
之前已请求此功能（请参阅this issue）。正如您所看到的，还有人正在研究它。他可能会在不久的将来提出拉动请求。我没有回顾他的变化，但一旦发生这种变化肯定会做。
现在，您可以让模型处理条件检查并将其与有序转换相结合，以省去频繁更新next_state函数指针的需要。由于您只是检查索引，因此可能如下所示：
from transitions import Machine
class AModel(object):
def __init__(self):
self.sv = 0 # state variable of the model
self.conditions = { # each state
'sA': 0,
'sB': 3,
'sC': 6,
'sD': 0,
}
def poll(self):
if self.sv >= self.conditions[self.state]:
self.next_state()
# setup model and state machine
model = AModel()
# init transitions model
list_of_states = ['sA', 'sB', 'sC', 'sD']
machine = Machine(model=model, states=list_of_states, initial='sA', ordered_transitions=True)
# begin main
for i in range(0, 10):
print('iter is: ' + str(i) + " -model state is:" + model.state)
model.sv = i
model.poll()
我假设每次索引增加时都会轮询模型。如果是这种情况，self.sv == 6和self.sv >= 6执行相同的操作（适用于sC到sD）。
但是，如果故意选择运算符，则可以更改模型条件检查以使用运算符值元组：
from transitions import Machine
import operator
class AModel(object):
def __init__(self):
self.sv = 0 # state variable of the model
self.conditions = { # each state
'sA': (operator.ne, None),
'sB': (operator.ge, 3),
'sC': (operator.eq, 6),
'sD': (operator.ne, None),
}
def poll(self):
op, value = self.conditions[self.state]
if op(self.sv, value):
self.next_state()
# setup model and state machine
model = AModel()
# init transitions model
list_of_states = ['sA', 'sB', 'sC', 'sD']
machine = Machine(model=model, states=list_of_states, initial='sA', ordered_transitions=True)
# begin main
for i in range(0, 10):
print('iter is: ' + str(i) + " -model state is:" + model.state)
model.sv = i
model.poll()
在这两种情况下，输出为：
iter is: 0 -model state is:sA
iter is: 1 -model state is:sB
iter is: 2 -model state is:sB
iter is: 3 -model state is:sB
iter is: 4 -model state is:sC
iter is: 5 -model state is:sC
iter is: 6 -model state is:sC
iter is: 7 -model state is:sD
iter is: 8 -model state is:sA
iter is: 9 -model state is:sB
但是，我再次假设可能出错的事情：我认为如果满足条件就改变状态就足够了。这就是条件的运作方式。但也许你每次轮询你的模型时都打算退出并输入状态。在这种情况下，您可以使用auto_transitions并使用getattr动态检索它们：
from transitions import Machine
class AModel(object):
def __init__(self):
self.sv = 0 # state variable of the model
self.conditions = { # each state
'sA': 0,
'sB': 3,
'sC': 6,
'sD': 0,
}
def poll(self):
if self.sv >= self.conditions[self.state]:
self.next_state() # go to next state
else:
getattr(self, 'to_%s' % self.state)() # enter current state again
def on_enter(self):
print('entered state %s' % self.state)
def on_exit(self):
print('exited state %s' % self.state)
# setup model and state machine
model = AModel()
# init transitions model
list_of_states = ['sA', 'sB', 'sC', 'sD']
machine = Machine(model=model, states=list_of_states, initial='sA',
ordered_transitions=True, before_state_change='on_exit',
after_state_change='on_enter')
# begin main
for i in range(0, 10):
print('iter is: ' + str(i) + " -model state is:" + model.state)
model.sv = i
model.poll()
为了简单起见，我添加了每次进入或退出状态时打印消息的功能。如果您使用记录器，则不需要这样做，因为transitions也会记录这些事件。
答案 1 :(得分：0)
我还没想出如何将它添加到过渡模块，但是我根据条件自动转换：
class StateMachine:
def __init__(self, name, states, transitions, initialState):
self.name=name
self.states=set()
self.transitions=set()
self.state=None
for s in states:
_s=State(s)
self.states.add(_s)
if self.state==None:
self.state=_s
elif s==initialState:
self.state=_s
for t in transitions:
# self.addTransition(t)
def addTransition(self, transition):
name=transition[0]
for s in self.states:
#fromState
if s.name==transition[1]:
fromState=s
#toState
elif s.name==transition[2]:
toState=s
#condition
condition=getattr(self, transition[3])
#action
if len(transition)==5:
action = getattr(self, transition[4])()
else:
action=self.passAction
t=Transition(name, fromState, toState, condition, action)
fromState.transitions.add(t)
def passAction(self):
print('pass!!!')
def run(self):
self.state=self.state.testTransitions()
def __repr__(self):
return self.name+':'+str(self.states)
class State:
def __init__(self, name='state'):
self.name=name
self.transitions=set()
def __repr__(self):
return self.name+':'+str(self.transitions)
def testTransitions(self):
state=self
for t in self.transitions:
if t.condition() is True:
t.action()
state=t.toState
return state
class Transition:
def __init__(self, name, fromState, toState, condition, action):
self.name=name
self.fromState=fromState
self.toState=toState
self.condition=condition
self.action=action
def __repr__(self):
return self.name
class TestSM(StateMachine):
def __init__(self, name, states, transitions, initialState):
StateMachine.__init__(self, name, states, transitions, initialState)
def testCondition(self):
print('testCondition!!!')
return True
states=['a', 'b', 'c']
transitions=[
['aTOb', 'a', 'b', 'testCondition'],
['bTOc', 'b', 'c', 'testCondition'],
['cTOa', 'c', 'a', 'testCondition'],
]
sm=TestSM('testSM', states, transitions, 'a')
for s in sm.states:
print(s.name)
print('fin')
为了运行状态机，只需运行'run'函数，例如：
sm.run()