State Machine Logic Block

Related Config File Sections
state_machines:
state_machine_states:
state_machine_transitions:

Related How To Guides
Integrating Logic_Blocks and Shows

“State machines” are a type of Logic Block where you can trigger state transitions based on the current state and an event.

Technically, this is a finite state machine as known from CS class.

Video about state machines:

This is an example:

##! mode: my_mode
state_machines:
  my_state:
    states:
      start:
        label: Start state
      step1:
        label:
        show_when_active:
          show: on
          show_tokens: None
        events_when_started: step1_start
        events_when_stopped: step1_stop
      step2:
        label:
    transitions:
      - source: start
        target: step1
        events: state_machine_proceed
      - source: step1
        target: step2
        events: state_machine_proceed2
        events_when_transitioning: going_to_step2
      - source: step2
        target: start
        events: state_machine_proceed3
      - source: step1, step2
        target: start
        events: state_machine_reset

This example is tested to be valid MPF config. Additionally, our integration test passed. Click to show the test and full config.

##! mode: my_mode
state_machines:
  my_state:
    states:
      start:
        label: Start state
      step1:
        label:
        show_when_active:
          show: on
          show_tokens: None
        events_when_started: step1_start
        events_when_stopped: step1_stop
      step2:
        label:
    transitions:
      - source: start
        target: step1
        events: state_machine_proceed
      - source: step1
        target: step2
        events: state_machine_proceed2
        events_when_transitioning: going_to_step2
      - source: step2
        target: start
        events: state_machine_proceed3
      - source: step1, step2
        target: start
        events: state_machine_reset
##! test
start_game
start_mode my_mode
mock_event going_to_step2
assert_str_condition start device.state_machines.my_state.state
post state_machine_proceed
assert_str_condition step1 device.state_machines.my_state.state
assert_event_not_called going_to_step2
post state_machine_proceed2
assert_str_condition step2 device.state_machines.my_state.state
assert_event_called going_to_step2

Storing the State in a Player Variable

If you want to store the state of your state machine in a player variable your can use a variable_player. You can then use it on slides or in places where conditions do not work (yet).

##! mode: my_mode
state_machines:
  my_state:
    states:
      start:
        label: Start state
      step1:
        label:
        show_when_active:
          show: on
          show_tokens: None
        events_when_started: step1_start
        events_when_stopped: step1_stop
      step2:
        label:
    transitions:
      - source: start
        target: step1
        events: state_machine_proceed
      - source: step1
        target: step2
        events: state_machine_proceed2
        events_when_transitioning: going_to_step2
      - source: step2
        target: start
        events: state_machine_proceed3
      - source: step1, step2
        target: start
        events: state_machine_reset

variable_player:
  "{device.state_machines.my_state.state}":
    my_player_var:
      action: set
      string: "{value}"

This example is tested to be valid MPF config. Additionally, our integration test passed. Click to show the test and full config.

##! mode: my_mode
state_machines:
  my_state:
    states:
      start:
        label: Start state
      step1:
        label:
        show_when_active:
          show: on
          show_tokens: None
        events_when_started: step1_start
        events_when_stopped: step1_stop
      step2:
        label:
    transitions:
      - source: start
        target: step1
        events: state_machine_proceed
      - source: step1
        target: step2
        events: state_machine_proceed2
        events_when_transitioning: going_to_step2
      - source: step2
        target: start
        events: state_machine_proceed3
      - source: step1, step2
        target: start
        events: state_machine_reset

variable_player:
  "{device.state_machines.my_state.state}":
    my_player_var:
      action: set
      string: "{value}"

##! test
start_game
start_mode my_mode
advance_time_and_run .1
mock_event going_to_step2
assert_str_condition start device.state_machines.my_state.state
assert_player_variable start my_player_var
post state_machine_proceed
advance_time_and_run .1
assert_str_condition step1 device.state_machines.my_state.state
assert_player_variable step1 my_player_var
assert_event_not_called going_to_step2
post state_machine_proceed2
advance_time_and_run .1
assert_str_condition step2 device.state_machines.my_state.state
assert_event_called going_to_step2
assert_player_variable step2 my_player_var

Monitorable Properties

For dynamic values and conditional events, the prefix for state machines is device.state_machines.<name>.

state

The state of this state machine as string. This will be one of your entries in your states section.