Confusion on State Machines

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1

Godot Version

Godot Version 4

Question

Hi guys this is a very stupid question . but I was experimenting with state machines and I stole this code from a tutorial https://www.youtube.com/watch?v=i0Y6anqiJ-g&t=264s now I didn’t understand it at first but I copied the code and started playing with it I understood the concept itself but I just cannot for the life of me figure out what i am doing wrong with the actual states themselves.

_____ State machine code checked with other videos and its pretty standard for a tutorial state machine

@iconiconiconicon(“res://Art/Icons/FSMSprite.png”)
extends Node
class_name FiniteStateMachine

var states : Dictionary = {}
var current_stat@export : St

@export ar current_state : State
@export var initial_state : State

func _ready():
for child in get_children():
if child is State:
states[child.name.to_lower()] = child
child.state_transition.connect(change_state)

if initial_state:
	initial_state.Enter()
	current_state = initial_state

#Call the current states update function continuosly
func _process(delta):
if current_state:
current_state.Update(delta)

#region State Management
#Use force_change_state cautiously, it immediately switches to a state regardless of any transitions.
#This is used to force us into a ‘death state’ when killed
func force_change_state(new_state : String):
var newState = states.get(new_state.to_lower())

if !newState:
	print(new_state + " does not exist in the dictionary of states")
	return

if current_state == newState:
	print("State is same, aborting")
	return
	
#NOTE Calling exit like so: (current_state.Exit()) may cause warnings when flushing queries, like when the enemy is being removed after death. 
#call_deferred is safe and prevents this from occuring. We get the Exit function from the state as a callable and then call it in a thread-safe manner
if current_state:
	var exit_callable = Callable(current_state, "Exit")
	exit_callable.call_deferred()

newState.Enter()

current_state = newState

func change_state(source_state : State, new_state_name : String):
if source_state != current_state:
#print("Invalid change_state trying from: " + source_state.name + " but currently in: " + current_state.name)
#This typically only happens when trying to switch from death state following a force_change
return

var new_state = states.get(new_state_name.to_lower())
if !new_state:
	print("New state is empty")
	return
	
if current_state:
	current_state.Exit()
	
new_state.Enter()

current_state = new_state

_____

Lets say i have two states Idle and Running, now do i make their class_names both States? I tried that and there was a (I am guessing) class naming error because you cant name both the same class so what am I doing wrong ?

here is the state code and its the same for both of them :

class_name State
extends Node

@export var parent : Player

@onready var animations = parent.get_node(“animations”)

@export var animation : String

func Enter():
animations.play(animation)

func Exit():
pass

signal state_transition

func Update(_delta:float):
pass

For both running and idle state its the code above

2

What problems are getting solved by using this “state machine”?

3

I am just experimenting with it if thats what you mean

4

Yeah but for what purpose?
Maybe you should fully follow through the tutorial first.

Btw, format your code properly using ``` tags.

5

I see thank you !

6

To actually answer the question:

You would make the class_names the actual state names, because class_name should always reflect the purpose of the class:

# idle.gd
class_name Idle
extends State

# running.gd
class_name Running
extends State

Where State is a class with the script you shared last.

This one 
class_name State
extends Node

@export var parent : Player

@onready var animations = parent.get_node(“animations”)

@export var animation : String

func Enter():
    animations.play(animation)

func Exit():
    pass

signal state_transition

func Update(_delta:float):
    pass

If you’re wondering about what the extends State is doing you might want to read up on inheritance.

  • Asking AI is usually a good way to get a very basic understanding of something
  • Godot docs:
  • Wikipedia (if you’re feeling up to it):

This way you can instantiate the classes Idle and Running as states. You have to leave out all the variables because they’re already declared in the base class State:

# idle.gd / state.gd
class_name Idle / State
extends State

func Enter():
    animations.play(animation)

func Exit():
    pass

func Update(_delta:float):
    pass