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C# Finite State Machine for Unity
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| using System; | |
| using System.Collections.Generic; | |
| using UnityEngine; | |
| /* Example usage: | |
| public FSM GameFSM = new(); | |
| private void Awake() | |
| { | |
| GameFSM.AddState("Init", | |
| onEnter: fsm => | |
| { | |
| print("Init"); | |
| fsm.ChangeState("Play"); | |
| } | |
| ); | |
| GameFSM.AddState("Play", | |
| onEnter: _ => print("Play"), | |
| onUpdate: fsm => | |
| { | |
| if (Input.GetKeyDown(KeyCode.Space)) | |
| fsm.Trigger("OnLevelCompleted"); | |
| }, | |
| onExit: _ => print("Exiting Play state"), | |
| triggers: new() | |
| { | |
| ("OnLevelCompleted", fsm => fsm.ChangeState("LevelCompleted")), | |
| ("OnPlayerDeath", fsm => fsm.ChangeState("GameOver")) | |
| } | |
| ); | |
| GameFSM.AddState("LevelCompleted", | |
| onEnter: _ => print("Level was completed") | |
| ); | |
| GameFSM.AddState("GameOver", | |
| onEnter: _ => print("Game Over!") | |
| ); | |
| GameFSM.ChangeState("Init"); // Set starting state | |
| } | |
| void FixedUpdate() | |
| { | |
| GameFSM.FixedUpdate(); | |
| } | |
| void Update() | |
| { | |
| GameFSM.Update(); | |
| } | |
| void LateUpdate() | |
| { | |
| GameFSM.LateUpdate(); | |
| } | |
| */ | |
| public class FSM | |
| { | |
| public string CurrentState = string.Empty; | |
| public Dictionary<string, Dictionary<string, Action<FSM>>> StatesTable = new(); | |
| public FSM AddState(string stateName, Action<FSM> onEnter = null, Action<FSM> onFixedUpdate = null, Action<FSM> onUpdate = null, Action<FSM> onLateUpdate = null, Action<FSM> onExit = null, List<(string triggerName, Action<FSM> action)> triggers = null) | |
| { | |
| if (StatesTable.ContainsKey(stateName)) | |
| { | |
| Debug.Log($"FSM AddState - State name ({stateName}) already exists."); | |
| return this; | |
| } | |
| else | |
| { | |
| string.Intern(stateName); | |
| } | |
| // Assign actions | |
| onEnter ??= DoNothing; | |
| onFixedUpdate ??= DoNothing; | |
| onUpdate ??= DoNothing; | |
| onLateUpdate ??= DoNothing; | |
| onExit ??= DoNothing; | |
| void DoNothing(FSM fsm) { } | |
| StatesTable.Add(stateName, new Dictionary<string, Action<FSM>> | |
| { | |
| ["OnEnter"] = onEnter, | |
| ["OnFixedUpdate"] = onFixedUpdate, | |
| ["OnUpdate"] = onUpdate, | |
| ["OnLateUpdate"] = onLateUpdate, | |
| ["OnExit"] = onExit | |
| }); | |
| // Add triggers | |
| triggers ??= new(); | |
| foreach (var (triggerName, action) in triggers) | |
| { | |
| StatesTable[stateName].Add(triggerName, action); | |
| string.Intern(triggerName); | |
| } | |
| return this; | |
| } | |
| public void ChangeState(string targetState) | |
| { | |
| if (!StatesTable.ContainsKey(targetState)) | |
| { | |
| Debug.Log($"FSM ChangeState - No matching state ({targetState}) in machine."); | |
| return; | |
| } | |
| if (!string.IsNullOrWhiteSpace(CurrentState)) | |
| StatesTable[CurrentState]["OnExit"](this); | |
| CurrentState = string.Intern(targetState); | |
| StatesTable[targetState]["OnEnter"](this); | |
| } | |
| public void Trigger(string triggerName) | |
| { | |
| if (!StatesTable[CurrentState].ContainsKey(triggerName)) | |
| { | |
| Debug.Log($"FSM Trigger - No matching trigger ({triggerName}) handler in the current state ({CurrentState})."); | |
| return; | |
| } | |
| StatesTable[CurrentState][triggerName](this); | |
| } | |
| public void FixedUpdate() | |
| { | |
| StatesTable[CurrentState]["OnFixedUpdate"](this); | |
| } | |
| public void Update() | |
| { | |
| StatesTable[CurrentState]["OnUpdate"](this); | |
| } | |
| public void LateUpdate() | |
| { | |
| StatesTable[CurrentState]["OnLateUpdate"](this); | |
| } | |
| } |
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