Godot Simple State

A clean and easy to use Finite State Machine (FSM) for Godot 3.x

Usage

1. Install the plugin

2. Enable the plugin

3. Add a SateMachine node to your character

   

4. Add any type of Node to the StateMachine as a child to create a new script

   

5. Attach a script to the node

6. Now at runtime you can change to a different state using $StateMachine.goto("state")

Example

The example project contains two states, idle and attack. The project will switch between each state automatically every 3 seconds.

State functionality

The state has a few functionalities, here is an example state:

extends Node2D

var Parent
var States

func _state_enter(arg or not):
    pass

func _state_exit():
    pass

If you call yield in _state_exit the StateMachine will wait for your yield to finish before entering the new state.

func _state_exit():
    yield(get_tree().create_timer(1), "timeout")

Note: Exit state

state will change to _exit when the state machine is exiting. Your state will also be queue-freed.

If running a long while loop in your state logic, be sure to check for States.is_current()

Reference

StateMachine

signal state_changed(new_state)

Emitted whenever the StateMachine changes state (but before _state_enter is called)

goto(state_name: String, args = null) change the state

args can be any or undefined

When an arg is passed, the argument will be pushed to the _state_enter function.

StateMachine.goto("attack")
StateMachine.goto("attack", some_character)
StateMachine.goto("attack", [some_character_a, some_character_b])

The last example would call this function in the attack state:

func _state_enter(some_characters: Array):
    ...

call(method: String, args = null) call a function on the current state (if exists)

StateMachine.call("some_method")
StateMachine.call("some_method", my_argument)
StateMachine.call("some_method", [my_arguments])

now(state: String)

Returns true if the current state matches state

if States.now("afraid"):
    # keep running away instead of stopping to look at something

has(state: String)

Returns true if exists in our state tree

if States.has("some-other-state"):
    # Do something

is_current()

Returns true only when called from a function inside the current state

if States.is_current():
    This can only be printed in the current state
    In any other state this will never be printed

restart(arg: any or none)

Restarts the current state This only calls "_state_enter" again it does not reset any variables

State

_state_enter(args or not) will be called when the state is entered (each time) An argument is only passed if one was passed. (StateMachine.goto("state", arg))

_state_exit() will be called when the state is left (each time)

If the following variables exist on your state, they will be injected with dependencies as follows:

Parent is the parent of StateMachine i.e. your character controller

States is the StateMachine

If they do not exist on your state, nothing will be injected.

Signals

You can connect signals directly to the StateMachine node using the following style:

They will be then automatically sent to the current active state if that state has the handler function defined.