/Godot-FiniteStateMachine

A plugin for Godot 4 that adds an implementation of the finite state machine pattern

Primary LanguageGDScriptMIT LicenseMIT

Finite State Machine plugin

A GDScript implementation of the finite state machine pattern.

Adds node types for finite state machines and states.

Installing the plugin in your project

The procedure is the same as other Godot plugins. See the Godot docs for a full explanation.

  1. Click the AssetLib tab at the top of the editor and look for Finite State Machine.

  2. Download the plugin and install the contents of the addons and the script_templates folders into your project's directory. You don't need the contents of the example folder.

  3. Go to Project -> Project Settings... -> Plugins and enable the plugin by checking "Enable".

It is also possible to install the plugin manually by downloading the zip archive from the Releases section.

Plugin contents

The plugin contains two script classes: FiniteStateMachine and StateMachineState. Both can be added to your scenes as nodes through the "Create New Node" menu.

Create node

The FiniteStateMachine node can be added as a child of your character's node and will handle the state machine's logic.

The StateMachineState class is an abstract class. You can extend this script to create your states.

Creating a state machine

Open the "Create New Node" menu and search for "FiniteStateMachine". Add this node in your character's scene.

State machine inspector

A state machine by itself does nothing, you need to create a script for a state. From the "Create script" menu, create a script that inherits from StateMachineState.

Create script

The script template downloaded with the plugin will generate some function stubs. You can now implement these functions to create a state.

class_name MyState
extends StateMachineState


# Called when the state machine enters this state.
func on_enter() -> void:
	pass


# Called every frame when this state is active.
func on_process(delta: float) -> void:
	pass


# Called every physics frame when this state is active.
func on_physics_process(delta: float) -> void:
	pass


# Called when there is an input event while this state is active.
func on_input(event: InputEvent) -> void:
	pass


# Called when the state machine exits this state.
func on_exit() -> void:
	pass

Once a state is created, you can add it as a child of the FiniteStateMachine node. Assign a state to the state machine from the inspector to set that as the initial state.

You can now change between states from your scripts by setting current_state or using the change_state function. See the comments in the scripts for a full explanation.

State machine scene

Additional information

Important note: Do not delete .godot/global_script_class_cache.cfg when this plugin is installed until Issue 81615 is resolved.