hsm.core.CallbackState

class CallbackState(name, callback, *args, **kwargs)

Bases: ProcessingState

State executing a given function while being active.

Methods

add_handler	Add a new event callback.
add_transition	Add a transition from self to target_state
execute	Method executed while this state is active
is_active
is_substate	Check whether the state is a substate of self.
request_preempt
ros_subscribe

Attributes

root	Get the root state in a states hierarchy.

add_handler(events, func, prepend=False)

Add a new event callback.

Parameters:

• trigger (str) – name of triggering event

• func (callable) – callback function

add_transition(events, target_state, condition=None, action=None, before=None, after=None)

Add a transition from self to target_state

All callbacks take two arguments - state and event. See parameters description for details.

It is possible to create conditional if/elif/else-like logic for transitions. To do so, add many same transition rules with different condition callbacks. First met condition will trigger a transition, if no condition is met, no transition is performed.

Parameters:

• target_state (State, None) – Target state. If None, then it’s an internal transition

• events (Iterable of Hashable) – List of events that trigger the transition

• condition (Callable) –

  Condition callback - if returns True transition may be initiated.

  condition callback takes two arguments:

  • state: Leaf state before transition

  • event: Event that triggered the transition

• action (Callable) –

  Action callback that is called during the transition after all states have been left but before the new one is entered.

  action callback takes two arguments:

  • state: Leaf state before transition

  • event: Event that triggered the transition

• before (Callable) –

  Action callback that is called right before the transition.

  before callback takes two arguments:

  • state: Leaf state before transition

  • event: Event that triggered the transition

• after (Callable) –

  Action callback that is called just after the transition

  after callback takes two arguments:

  • state: Leaf state after transition

  • event: Event that triggered the transition

execute(event=None)

Method executed while this state is active

The return value of this function triggers a corresponding event.

is_substate(state)

Check whether the state is a substate of self.

Also self is considered a substate of self.

Parameters:

state (State) – State to verify

Returns:

True if state is a substate of self, False otherwise

Return type:

bool

property root

Get the root state in a states hierarchy.

Returns:

Root state in the states hierarchy

Return type:

State