Unity Finite State Machine

State machine is a very effective way to manage game entities with complex behaviours based on time and/or various states. This is a simple, performant implementation of FSM.

See [http://minhhh.github.io/posts/finite-state-machine-for-unity](Finite state machine for Unity) for a more detailed discussion of FSM in Unity.

How to use

CustomFSMManager is a Component that facilitates your custom FSM. It does not represent states itself, instead, it uses reflection to look at functions of the main Component and determines which function should be called when switching states.

First, you create an Enum which represents the states like so:

public enum MyState
{
    Start,
    Loop,
    End
}

Next, you define a MonoBehaviour that will represents the Entity with those states. This MonoBehaviour will contain a reference to a CustomFSMManager, which in turn will manage the MonoBehaviour's states. 'In the Start or Awake function, you add the following code to initialize the CustomFSMManager according to the states defined in MyState:

CustomFSMManager customFSMManager;

 void Start ()
{
    customFSMManager = gameObject.AddComponent<CustomFSMManager>();
    customFSMManager.Initialize(typeof(MyState), this);

    customFSMManager.StateMachineChange(MyState.Loop); // this is optional
}

Initially, the CustomFSMManager will start with state corresponding to the integer 0, so optionally you can call customFSMManager.StateMachineChange right away.

The CustomFSMManager will update itself by default, so if you want more control, you can force it to not update itself, and call CustomFSMManager.StateMachineUpdate manually. To do this, you can call Initialize (T, comp, false), passing false to the third parameter.

Next, you define Enter, Exit, Update functions for each necessary states. These functions will be found using reflection. For example, the state Start will correspond to the following functions: StateMachineExit_Start, StateMachineEnter_Loop, StateMachineEnter_Update.

The signature of Start and Exit functions is: void StateMachineEnter_XXX (Enum state, Dictionary<string, object> options = null). The signature of the Update function is: void StateMachineUpdate_XXX (float deltaTime)

You can also call SetStopUpdate to temporarily stop the update of the state machine.

An sample scene is included in the Assets folder.