State Machine not switching State

Unity Engine
,
1

I’m following along a tutorial about State Machines and trying to implement it. I have a simple setup now but it is not working. Well I can log from the HeroIdle, but when changing the move float, I do not switch to the HeroRun state. Can anyone help me why that is?

public interface IState
{
    void Tick();
    void OnEnter();
    void OnExit();
}

public class StateMachine
{
   private IState _currentState;
   private Dictionary<Type, List<Transition>> _transition = new Dictionary<Type, List<Transition>>();
   private List<Transition> _currentTransitions = new List<Transition>();
   private List<Transition> _anyTransitions = new List<Transition>();
   private static List<Transition> EmptyTransitions = new List<Transition>(0);

   public void Tick()
   {
      var transition = GetTransition();
      if (transition != null)
         SetState(transition.To);
      _currentState?.Tick();
   }

   public void SetState(IState state)
   {
      if (state == _currentState)
         return;
      _currentState?.OnExit();
      _currentState = state;

      _transition.TryGetValue(_currentState.GetType(), out _currentTransitions);
      if (_currentTransitions == null)
      {
         _currentTransitions = EmptyTransitions;
      }
      _currentState.OnEnter();
   }

   public void AddTransition(IState from, IState to, Func<bool> predicate)
   {
      if (_transition.TryGetValue(from.GetType(), out var transitions) == false)
      {
         transitions = new List<Transition>();
         _transition[from.GetType()] = transitions;
      }
      transitions.Add(new Transition(to, predicate));
   }

   public void AddAnyTransition(IState state, Func<bool> predicate)
   {
      _anyTransitions.Add(new Transition(state, predicate));
   }


   private class Transition
   {
      public Func<bool> Condition { get; }
      public IState To { get; }

      public Transition(IState to, Func<bool> condition)
      {
         To = to;
         Condition = condition;
      }
   }

   private Transition GetTransition()
   {
      foreach (var transition in _anyTransitions)
         if (transition.Condition())
            return transition;

      foreach (var transition in _currentTransitions)
         if (transition.Condition())
            return transition;

      return null;
   }
}

public class Hero : MonoBehaviour
{
    private StateMachine _stateMachine;
    private float move = 0f;
   
    private void Awake()
    {
        var animator = GetComponent<Animator>();
        _stateMachine = new StateMachine();
        var heroIdle = new HeroIdle(this, animator);
        var heroRun = new HeroRun(this, animator);
       
        _stateMachine.SetState(heroIdle);
       
        At(heroIdle, heroRun, IsRunning());
        At(heroRun, heroIdle, IsNotRunning());

        void At(IState from, IState to, Func<bool> condition) => _stateMachine.AddTransition(from, to, condition);
        Func<bool> IsRunning() => () => move != 0;
        Func<bool> IsNotRunning() => () => move == 0;
    }

    void Update()
    {
        _stateMachine.Tick();
        move = Input.GetAxisRaw("Horizontal");
    }
}

public class HeroIdle : IState
{
    private readonly Hero _hero;
    private readonly Animator _animator;

    public HeroIdle(Hero hero, Animator animator)
    {
        _hero = hero;
        _animator = animator;
    }

    public void Tick()
    {
        Debug.Log("we are idle");
    }

    public void OnEnter()
    {
       
    }

    public void OnExit()
    {
        throw new System.NotImplementedException();
    }
}

public class HeroRun : IState
{
    private readonly Hero _hero;
    private readonly Animator _animator;

    public HeroRun(Hero hero, Animator animator)
    {
        _hero = hero;
        _animator = animator;
    }

    public void Tick()
    {
        Debug.Log("we are running");

    }

    public void OnEnter()
    {
        throw new System.NotImplementedException();
    }

    public void OnExit()
    {
        throw new System.NotImplementedException();
    }
}
2

Don’t stop logging with that! Go nuts.

You must find a way to get the information you need in order to reason about what the problem is.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also put in Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://discussions.unity.com/t/839300/3

A side note about FSMs:

This is my position on finite state machines (FSMs):

https://discussions.unity.com/t/834040/6

I’m kind of more of a “get it working first” guy.

Your mileage may vary.

1 Like
3

After a lot of debugging, I found out it was the f I forgot to add to Func IsRunning() => () => move != 0f

2 Likes