ServiceRegistry.cs

using System.Collections.Generic;

public static class ServiceRegistry
{
    
    // This is a Dictionary (a type of list) of all objects currently registered, by their type
    private static Dictionary<System.Type, object> _services = new();
    
    // Usage: ServiceRegistry.Register(this)
    // Please only register one instance of each type
    public static void Register(object obj)
    {
        _services.Add(obj.GetType(), obj);
    }
    
    public static void UnRegister(object obj)
    {
        _services.Remove(obj.GetType());
    }
    
    // Usage: Foo foo = ServiceRegistry.Get<Foo>();
    public static T Get<T>()
    {
        object system;
        // Try to get a system out of our Dictionary
        _services.TryGetValue(typeof(T), out system);
        // If it fails, throw an error. No class of that type was registered
        if (system == null) Debug.LogError("Could not find system of type " + typeof(T));
        // Return the system (can be null)
        return (T)system;
    }
}