How to subscribe to events in C# inside an instance that are dispatched from another instance in Unity?

Question

Let's assume I have a class which does not inherit from MonoBehavior that looks like this:

public interface IApplication
{
    void run();
}

public class Application : IApplication
{
    public static IServiceManager serviceManager;
    public delegate void ApplicationStartedEvent(object source, EventArgs args);
    public event ApplicationStartedEvent applicationStartedEvent;

    public void run()
    {

    }

    protected virtual void OnApplicationStarted()
    {
        if (applicationStartedEvent != null)
        {
            applicationStartedEvent(this, EventArgs.Empty);
        }
    }
}

And a Unity controller which is a MonoBehavior like this:

public class LoginController : MonoBehaviour 
{
    void Start()
    {
        Hide();
    }

    public void OnApplicationStarted(object source, EventArgs e)
    {
        Show();
    }

    public virtual void Show()
    {
        gameObject.SetActive(true);
    }

    public virtual void Hide()
    {
        gameObject.SetActive(false);
    }
}

How do I connect those two?

Let's assume I have the following Bootstrap code:

public class Setup : MonoBehaviour
{
    Application application;

    void Awake()
    {
        application = new Application();
        application.run();
    }
}

How do I make my LoginController OnApplicationStarted method run when Application run method is being invoked or Dispatch an event that is ApplicationStartedEvent.

An example of how do I think EventManager should look like:

addEventListener(string eventName, Callback callback)

dispatchEvent(Event event)

Here's how ull use it in the LoginController:

EventManager.addEventListener("ApplicationStarted", this.OnApplicationStarted)

And here's how ull use it in the Application:

public void run()
{
    EventManager.dispatchEvent(new ApplicationStartedEvent());
}

Obviously it's just an idea and not have to be the same syntax.

EDIT: I think I have found something that is almost similar to what I am looking for: http://wiki.unity3d.com/index.php/Advanced_CSharp_Messenger

Answer 1

How do I make my LoginController OnApplicationStarted method run when Application run method is being invoked or Dispatch an event that is ApplicationStartedEvent.

Create an EventManager script that can register and un-register events. This functions should take ApplicationStartedEvent as a parameter. Add one more function that can be used to invoke the subsribed events.

You can then subsribe to the events from the other scripts such as the LoginController script. The subscription should be done in the OnEnable and OnDisable function.

Events can then be invoked from the run() function in the Application script.

Very important:

Please rename your Application script to Application2 or something else. There is a Unity API named Application and you will run into compile-time error if you ever use functions from this class.

I will use Application2 instead of Application in this solution.

EventManager.cs:

Please attach this to an Empty GameObject

public class EventManager : MonoBehaviour
{
    private static EventManager localInstance;
    public static EventManager Instance { get { return localInstance; } }

    private void Awake()
    {
        if (localInstance != null && localInstance != this)
        {
            Destroy(this.gameObject);
        }
        else
        {
            localInstance = this;
        }
    }

    public delegate void ApplicationStartedEvent(object source, EventArgs args);
    private event ApplicationStartedEvent applicationStartedEvent;


    public void dispatchEvent(object source, EventArgs args)
    {
        foreach (ApplicationStartedEvent runEvent in applicationStartedEvent.GetInvocationList())
        {
            try
            {
                runEvent.Invoke(source, args);
            }
            catch (Exception e)
            {
                Debug.LogError(string.Format("Exception while invoking" + runEvent.Method.Name + e.Message));
            }
        }
    }

    public void registerEvent(ApplicationStartedEvent callBackFunc)
    {
        applicationStartedEvent += callBackFunc;
    }

    public void unRegisterEvent(ApplicationStartedEvent callBackFunc)
    {
        applicationStartedEvent -= callBackFunc;
    }
}

Application2.cs:

public class Application2 : IApplication
{
    public void run()
    {
        OnApplicationStarted();
    }

    protected virtual void OnApplicationStarted()
    {
        EventManager.Instance.dispatchEvent(this, EventArgs.Empty);
    }
}

LoginController.cs:

public class LoginController : MonoBehaviour
{

    void Start()
    {
        Hide();
    }

    public void OnApplicationStarted(object source, EventArgs e)
    {
        Show();
    }

    public virtual void Show()
    {
        gameObject.SetActive(true);
    }

    public virtual void Hide()
    {
        gameObject.SetActive(false);
    }

    void OnEnable()
    {
        //Subscribe to event
        EventManager.Instance.registerEvent(OnApplicationStarted);
    }

    void OnDisable()
    {
        //Un-Subscribe to event
        EventManager.Instance.unRegisterEvent(OnApplicationStarted);
    }
}