How to connect different types of nodes through signals?

slamjam29

My current project revolves around the player(KinamaticBody2D) entering an Area2D to collect "ammo", but said Player can only do this once at a time, and each time he does so it's supposed to send him to a different state that ensures he can't collect more until he uses the ammo. My solution to this is to have the Area2D emit a signal to the Player, and the Player is supposed to receive it as a trigger to the next state. The problem is that I'm struggling to understand how these signals are supposed to be implemented, and nothing I've tried worked so far. Here's the signals I've tried:

Area2D:

		signal Area
		
		func _on_Area2D_body_entered(body):
				if body.name == "Player":
					emit_signal("Area")

Player:

		func ready():
		$Area2D.connect("body_entered", self, "_on_Player_body_entered")
		
		func on_Player_body_entered():
			if on_Player_body_entered():
				state = STATE_B

Is there anything I'm doing wrong here?

TwistedTwigleg

Have you connected the Area signal to the player? You can connect it using code like this in _ready:

func _ready():
	$Area2D.connect("Area", self, "on_area_emitted")

func on_area_emitted():
	print ("Area signal emitted!")

slamjam29

@TwistedTwigleg said: Have you connected the Area signal to the player? You can connect it using code like this in _ready:
func _ready():
	$Area2D.connect("Area", self, "on_area_emitted")

func on_area_emitted():
	print ("Area signal emitted!")

I tried it, but it didn't work sadly. The output just says "Node not found: Area2D" and nothing gets printed when I tried going into the Area2D.

DaveTheCoder

"Node not found: Area2D"

The reference $Area2D only works if the node named Area2D is a direct child of the node to which that script is attached. If Area2D is elsewhere in the scene tree, you need to use a different path.

slamjam29

@DaveTheCoder said: The reference $Area2D only works if the node named Area2D is a direct child of the node to which that script is attached. If Area2D is elsewhere in the scene tree, you need to use a different path.

Do you know what path I need to use exactly? Because the Area2D IS a separate node from the player, I was just trying have the Player receive whatever signal the Area2D was trying to emit, if possible.

DaveTheCoder

What's the path from the root of the scene tree to Area2D?

TwistedTwigleg

You could also use an exported NodePath and then set the path to the Area2D in the Godot editor. You’d just need code like this:

export (NodePath) var path_to_area
var area_node

func _ready():
	area_node = get_node(path_to_area)
	area_node.connect(“Area”, self, “on_area_emitted”)

func on_area_emitted():
	print (“Area signal emitted!”)

After assigning the script, you should be able to click the node and in the inspector there should be a NodePath you can set. Once set to the Area2D node, it should work as expected.

slamjam29

@DaveTheCoder said: What's the path from the root of the scene tree to Area2D?

"root/World/Area2D"? Or am I thinking of something else?

DaveTheCoder

If World is the top level node, then you could use this: $"/root/World/Area2D".connect("Area", self, "on_area_emitted")

Or you could use TwistedTwigleg's solution.

slamjam29

@TwistedTwigleg said: You could also use an exported NodePath and then set the path to the Area2D in the Godot editor. You’d just need code like this:
export (NodePath) var path_to_area
var area_node

func _ready():
	area_node = get_node(path_to_area)
	area_node.connect(“Area”, self, “on_area_emitted”)

func on_area_emitted():
	print (“Area signal emitted!”)
After assigning the script, you should be able to click the node and in the inspector there should be a NodePath you can set. Once set to the Area2D node, it should work as expected.

I think I might be doing this wrong, because I'm just getting errors for the nodepath. Specifically I tried "export (NodePath) var $root/World/Area2D" and getting "error: Expected an identifier for the member variable name".

@DaveTheCoder said: If World is the top level node, then you could use this: $"/root/World/Area2D".connect("Area", self, "on_area_emitted")

Or you could use TwistedTwigleg's solution.

This doesn't really work either. It just brings me back to square one where the player isn't receiving the signal.

slamjam29

Well, I decided to just give up on this entirely and go for an alternative route. Instead now I'm using another Area2D attached to the player itself as a sort of hitbox that detects other Area2D's. Works well enough, I just need to figure out how to get the Area to recognize names/individual Area2D's through "on_area_entered". Is there any way to do this without getting errors?

DaveTheCoder

The "area_entered" signal passes the other Area2D as a parameter. You can get the name of the Area2D from that (area.name). https://docs.godotengine.org/en/stable/classes/class_area2d.html#signals

I wonder if a CollisionShape2D as a child of the ammo would be more suitable for your objective.

This a code snippet from a demo project that uses that approach for picking up Potions by the Player:

	func _on_Potion_body_entered(body: Node) -> void:
 		if body.name == "Player":
    		body.add_potion()

slamjam29

@DaveTheCoder said: The "area_entered" signal passes the other Area2D as a parameter. You can get the name of the Area2D from that (area.name). https://docs.godotengine.org/en/stable/classes/class_area2d.html#signals

I wonder if a CollisionShape2D as a child of the ammo would be more suitable for your objective.

This a code snippet from a demo project that uses that approach for picking up Potions by the Player:
	func _on_Potion_body_entered(body: Node) -> void:
 		if body.name == "Player":
    		body.add_potion()

I've been trying this out, but it's very odd. I used a similar code like so:

		func _on_Area2D_area_entered(body: Node) -> void:
			if Area2D.name == "Area":
				print("Area")
			else:
				print("Not Area")

And made a separapte Area2D node with a different name. Not only did it not pick up or print the original Area, but the NotArea was somehow able to print despite that.

DaveTheCoder

Try printing Area2D.name and body.name at the beginning of the function.

slamjam29

@DaveTheCoder said: Try printing Area2D.name and body.name at the beginning of the function.

I think you lost me here, I thought I was already doing that. Is it alright if I ask for example of what you mean?

DaveTheCoder

func _on_Area2D_area_entered(body: Node) -> void:
    print("Area2D.name=%s, body.name=%s" % [Area2D.name, body.name])

slamjam29

@DaveTheCoder said: func _on_Area2D_area_entered(body: Node) -> void: print("Area2D.name=%s, body.name=%s" % [Area2D.name, body.name])

I'm sorry, but this didn't work either. It didn't print the first Area and the NotArea just had an error.