New Playmode Options: No Domain Reload vs. Unique Entities & Event Handlers

[thygrrr]

What is the current best practice to use Entitas Teardown() / Contexts.Reset() / ... in conjunction with the new playmode options that are in Unity 2020?

The problem is, that unique entities stay alive; as do the handlers for EntityLinks (or specifically, Events that then try to access GameObjects that are Unity null / destroyed)

I have tried to work with Script Execution Order and OnApplicationQuit() on my main controller, but... UnityView components get destroyed befor and after the context is being reset. So either I get the "detected retained entities" issue, or Unity's "trying to access a destroyed GameObject" error.

What kind of seems to work, but feels very hacky, is resetting the contexts on Start():

        private void Start()
        {
            _contexts = Contexts.sharedInstance;
            _contexts.Reset();

and catching the edge case where a UnityView is destroyed:

        private void OnDestroy()
        {
            //UnityEngine.Debug.Log($"Destroying view {gameObject.name}, linked to {LinkedEntity}");
            if (LinkedEntity != null)
                gameObject.Unlink();
        }

... the latter feels like an inappropriate re-inversion of control, and can have unwanted side effects if something that's not the ~~end of the world~~ Application quit kills the gameobject.

[thygrrr]

To clarify, object destruction order on application termination appears (kind of naturally/obviously) to be largely detached from script execution order, or occurs in several stages! But OnApplicationQuit() is invoked before all of these. You do not get another tick in between, though.

[mrobaczyk]

In my project in test's Teardown we do:

• unlink all gameobjects
• deactivate entitas systems
• clear scene (destroy gameobjects, clear DontDestroyOnLoad scene)
• destroy all entities
• reset entitas contexts
• activate contexts indices

[roygear]

Here is my solution :

Add below method to https://github.com/sschmid/Entitas-CSharp/blob/master/Addons/Entitas.CodeGeneration.Plugins/Entitas.CodeGeneration.Plugins/Context/CodeGenerators/ContextsGenerator.cs

    public static Contexts CreateNewInstance()
    {
        _sharedInstance = new Contexts();
        
        return _sharedInstance ;
    }

Recompile Entitas.CodeGeneration.Plugins

Then call this method before any entitas's call.