Passing nodes from a list

TheHeartless

I have a simple game which the main plot is two display RigidBodies (using visible = true), two at a time. After they are gone, due to the action performed by the player, another pair shows up. This scheme should go on as long as I support the RigidBodies. In the game structure, all RigidBodies are contained in a Control node. When I start the game, in the I create the list of nodes by invoking $Control.get_children() and passing it to the onready variable node_list (onready var node_list + $Control.get_children())

So far I have:

ROOT-
  	|
	Control - 
  			| 
			RigidBody_1
 			RigidBody_2
			(...)
			RigidBody_6

To show the node during game play I just have a simple function, node_show(), which code is as follows:

func node_show():
	node_1 = node_list.pop_front()	
	node_2 = node_list.pop_front()
	node_1.visible = true
		if node_1.visible == true:
			iteration +=1 				# A chec to count number od displayed nodes
	node_2.visible = true
		if node_2.visible == true:
			iteration +=1

Each time the RigidBody is triggered by the player in the scene, it plays an animation which, through the animation_finished native godot signal, triggers the self.queue_free() function to remove the node from the tree, free the game canvas and also pass a signal to the main scene that the node_show() can start and pick two new node from the list. So basically, I though it would work but it really behaves extremely funny. As initially the node_list contains six rigid bodies, the first run of the nod_show(), creates two nodes, 1 and 2, leaving the list with four RigidBodies, simple. The game goes, I react with the RigidBodies in the scene, they are removed and the node_show() is triggered to access the list, now with just four RigidBodies, passing two new nodes to the main scene and leaving two last nodes in the main node_list. But now what I see is something like this:

node_list = {[RigidBody2D:1315], [Deleted Object]]

Somehow the list has deleted bodies there, why would that happen? I would gladly welcome an at least hypothetical explanation as I believed this should be super simple but I can't pass this issue by myself. Is there a better way to approach such simple handling of nodes?

Erich_L

I fail to see the need for the list. Why not just instantiate two of the nodes you need, add them to the scene tree when you need them, and calling queue_free() when you’re done with them?

TheHeartless

@Erich_L said: I fail to see the need for the list. Why not just instantiate two of the nodes you need, add them to the scene tree when you need them, and calling queue_free() when you’re done with them?

I need the list as I intend to extend the amount of RigidBodies as I prepare new characters. I instantiate the RigidBodies in pairs so I though passing them from a list would be logical.

I have the nodes "in-place" present in the scene tree already so now I don't need to add them, I think at least, and this is the reason I just toggle the visibility of the node in the node_show() function.

cybereality

So, this line does nothing.

    node_1.visible = true
        if node_1.visible == true:

You just set node_1 to visible, so the if is always true and not needed.

Keeping the nodes themselves in the list is probably a bad idea in terms of garbage collection. So if you remove an object (using queue_free) but still keep a reference to it in the list, then it will exist forever, which is why it shows up as a deleted reference.

The list could work, but you should save scenes to instantiate, not existing nodes themselves. So create your rigid body scenes (you can make a few variations, or have 1 base scene that you pass parameters into that changes the graphics or behavior, etc.). Then in node_show you use instance() to create the node instance and then use add_child to add it to the game. Later when you are done you call remove_child and then queue_free and it will be deleted. I think that should work.

TheHeartless

@cybereality said: So, this line does nothing.
    node_1.visible = true
        if node_1.visible == true:
You just set node_1 to visible, so the if is always true and not needed.

Keeping the nodes themselves in the list is probably a bad idea in terms of garbage collection. So if you remove an object (using queue_free) but still keep a reference to it in the list, then it will exist forever, which is why it shows up as a deleted reference.

The list could work, but you should save scenes to instantiate, not existing nodes themselves. So create your rigid body scenes (you can make a few variations, or have 1 base scene that you pass parameters into that changes the graphics or behavior, etc.). Then in node_show you use instance() to create the node instance and then use add_child to add it to the game. Later when you are done you call remove_child and then queue_free and it will be deleted. I think that should work.

In the node_show() I use the .pop_front() method which "removes and returns the first element of the array" so there shouldn't be any junk in the list left afterwards, I believe. Especially when after running the node_show() once on the original list, , the nodes 1 and 2 are created and the list contains the last 4 remaining nodes.

I agree with Your option to use several scenes, I did that before and it worked, I just hoped to managed all of this from just one scene. I never tried to pass parameters like You mention, this is quite new to me.