Provide a way to reference instances of the same object (Instance Groups)

[tristanbob]

Is it correct to say that one weakness in GDevelop is that it is impossible to control interaction between instances of the same object? When using ForEach, you can only reference the instance that is currently in the loop. Can we think of a way to allow referencing other instances of the same object?

I ran into this problem with my Physics Chains extension. I had to use two different objects that connected ObjectA to ObjectB. I could not make an event that connected InstanceA to InstanceB.

What if we make a new Action that saves the currently picked instances with a Name that can be used later? (This Name functions as a temporary Instance Group.)

<previous code assigns an "ID" object variable to every instance>

EVENT:
 - Condition:  MyObject.Variable(ID)=1
 - Action:  Picked instances of "MyObject" can be referenced as "FirstInstance"
  
EVENT:
 - Condition:  MyObject.Variable(ID)=2
 - Action:  Picked instances of "MyObject" can be referenced as "SecondInstance"

EVENT:
 - Condition:  Distance between "FirstInstance" and "SecondInstance" is less than 10 pixels
 - Action:  Put "FirstInstance" around "SecondInstance" at a distance of 10 pixels and angle 0.

Would this idea be helpful? Is there a better way to provide this functionality?

[Bouh]

@D8H you face it with that problem too for one of your game isn't?

[D8H]

Yes, I think I face the same limitation to link the bubbles to form a grid for the B-a-M example. I did the same as Tristan and used 2 objects. It makes the code hard to understand.
I started this discussion: #2653
@tristanbob is it really the same subject?

[tristanbob]

@D8H yes, we are talking about the same thing! However, I didn't see any concrete solutions on your thread.

What do you think of my idea of using an Action to dynamically create an Instance Group based on the currently picked instances? This Instance Group can then be used like a normal Object/Object Group in Conditions and Actions.

[D8H]

I think it's what Florian called "Define OtherEnemy from Enemy" in this comment: #2653 (reply in thread)

Yes, I think this is something that needs a lots of thinking to be easy to understand and future proof and that's why there isn't really a solution in the discussion.

[4ian]

Yeah I believe this is the same need/discussion and potential solution as in #2653
Let's consolidate the discussion into one?

[tristanbob]

Of course. I make my comments on #2653.