Godot Pushdown Automaton FSM (Finite State Machine)
This is a FSM for Godot that is purely code-only (no editor plugin), and implements a stack (Pushdown Automaton).
extends Node2D
const StateMachine = preload("res://addons/fsm/StateMachine.gd")
const IdleState = preload("IdleState.gd")
# Create new state machine factory
var sm: StateMachine = StateMachine.new()
func _ready() -> void:
sm.target = self
sm.default_state = sm.state_create(IdleState)# Set the state machine's target (recursively sets on states)
sm.target = $Player
# Get state machine's target object
var player = sm.target# Set the state machine's current state. This really should be called internally by the state machine only.
var state = sm.get_state()The transition method of the state machine will validate that the id passed is a valid state. It will call the current state's _on_leave_state callback if implemented. It will then call the to state's _on_enter_state method.
# Transition to new state
sm.transition("patrol")The state manager exposes callback methods for _process(delta), _physics_process(delta), and _input(event). Calls to these methods are proxied down to the current state's method if it has implemented them.
# State machine callbacks which are proxied down to the current state object
sm._physics_process(delta)
sm._process(delta)
sm._input(event)
sm._on_enter_state()
sm._on_leave_state()Each state stores its own name.
var sm = StateMachine.new()
sm.target = $Player
sm.default_state = sm.create_push(IdleState)
var state = IdleState.new()
state.sm = sm
state.id = "idle"
var state_id = state.idThe state and state machine have a target object, which is assumed to be where any extra required context is coded against.
var smf = StateMachineFactory.new()
var sm = smf.create()
var state = IdleState.new()
state.state_machine = sm
state.id = "idle"
state.target = $Player
var player = state.targetA state class can implement callbacks for _process(delta), _physics_process(delta), _input(event), _on_enter_state(), and _on_leave_state().
extends "res://addons/fsm/StateMachine.gd".State
var memory = 0
func _init().():
physics_process_enabled = true
func _physics_process(delta: float) -> void:
scan_for_enemy(delta)
move_to_random(delta)
func scan_for_enemy(delta: float) -> void:
pass
func move_to_random(delta: float) -> void:
# some logic to move to a random location
...
# Transition to idle state if we have reached our destination
if arrived_at_location():
state_machine.transition("idle")
func _on_enter_state() -> void:
memory = 100Code borrowed from https://gitlab.com/reefpirate/finite_stack_machine/-/tree/master and then updated/refactored in alignment with godot-finite-state-machine, including example/demo.