create-state-machine

Create State Machine

Generate a node-based FSM. Compared to class-based / dictionary-based FSMs:

✅ Each state is a Node — visible in scene tree, Inspector-tweakable ✅ States can have their own children (timers, animation refs) ✅ Transitions go through a single signal — easy to log/debug ✅ Substituting a state for testing = swap a node

Files

scripts/state_machine/state_machine.gd

class_name StateMachine
extends Node
## Holds State child nodes; forwards engine callbacks to current state.
## States transition by emitting `transitioned(next_state_name)`.

signal state_changed(old: StringName, new: StringName)

@export var initial_state: NodePath
@export var debug: bool = false

var current_state: State
var states: Dictionary[StringName, State] = {}

func _ready() -> void:
    for child in get_children():
        if child is State:
            states[StringName(child.name)] = child
            child.transitioned.connect(_on_state_transitioned)
    if initial_state:
        current_state = get_node(initial_state) as State
    elif not states.is_empty():
        current_state = states.values()[0]
    if current_state:
        current_state.enter({})

func _process(delta: float) -> void:
    if current_state:
        current_state.update(delta)

func _physics_process(delta: float) -> void:
    if current_state:
        current_state.physics_update(delta)

func _unhandled_input(event: InputEvent) -> void:
    if current_state:
        current_state.handle_input(event)

func change_state(target: StringName, payload: Dictionary = {}) -> void:
    if not states.has(target):
        push_warning("StateMachine: missing state '%s'" % target)
        return
    var old := StringName(current_state.name) if current_state else &""
    if current_state:
        current_state.exit()
    current_state = states[target]
    if debug:
        print("[FSM] %s -> %s" % [old, target])
    state_changed.emit(old, target)
    current_state.enter(payload)

func _on_state_transitioned(target: StringName, payload: Dictionary) -> void:
    change_state(target, payload)