class Main
{
    private Holder _holder;

    private void Start()
    {
        _holder.DoSmth(new Move());
    }
}

class Holder: MonoBehaviour
{
    public void DoSmth(IState state)
    {
        state.Process();
    }
}

interface IState
{
    void Process();
}

struct Move : IState
{
    public void Process()
    {
        throw new System.NotImplementedException();
    }
}

struct FindFood : IState
{
    public void Process()
    {
        throw new System.NotImplementedException();
    }
}