Lots of googling and I'm still not grasping what is probably a simple solution.
Scene: "Main". Contains a TileMap "Grid" with a script attached to it "Grid.gd".
Scene: "Player". Contains a KinematicBody2D "Player" with a script attached to it "Player.gd"
In Player.gd, I need to call a method in Grid.gd "_Calculate", pass it two variables, and have it return one variable.
var vNewPosition = Grid._Calculate(vPlayer, vInputDirection)
Error: The identifier "Grid" isn't declared in the current scope.
Obiously I need to reference the Grid.gd script somewhere to access it, but none of the many examples I have tried work.
Thanks in advance,
Josh
Given that
The Main scene has an instance of the Player scene
And
In Player.gd, I need to call a method in Grid.gd "_Calculate", pass it two variables, and have it return one variable.
I'll give you a few options.
The bad way
If Player knows the node path to Grid, it could use get_node to get it.
onready var _grid = get_node("../../grid")
Or something like that.
And then use it:
var vNewPosition = _grid._Calculate(vPlayer, vInputDirection)
This approach is, of course, not recommended. It will break if the node path is wrong.
The common way
Assuming Player does not know the node path (which is more likely), you can export a NodePath variable in Player.gd and use it to get the Grid:
exprort var grid_path:NodePath
onready var _grid = get_node(grid_path)
Then you need to set the Grid Path property in the Main scene to Grid.
This approach is better than the prior one, in that it does not depend on the path to Grid. However it still depends on a Grid being there. If Player makes no sense when there is no Grid, this approach is OK.
The good way
If Grid may or may not be there, and we want Player to work regardless, we can tweak the above approach:
exprort var grid_path:NodePath
onready var _grid = get_node_or_null(grid_path)
And remember to check if grid is null before using it:
if grid == null:
return # or whatever
var vNewPosition = grid._Calculate(vPlayer, vInputDirection)
Or like this:
var vNewPosition = grid._Calculate(vPlayer, vInputDirection) if grid != null else null
Which also allows us to specify a default value that vNewPosition will take when there is no grid (the null at the end of the line). And thus you can have the Player work when there is no Grid, and when there is it will use, and regardless of where (because Main tells it where it is).
This solution is not completely decoupled, because Player still knows grid is a thing that has _Calculate. Also we presume there is zero or one, not multiple. I can think of a way to approach that, but decoupling for the sake of decoupling is unnecessary. I'm calling this good enough for your use case. Yet, let me know if you want the over-engineered way.
Related
I want to move my Player node (KinematicBody2D) from one scene to another. My code successfully moves Node2D node, but fails with KinematicBody2D node.
I have two Location scenes (inheriting from base Location scene) with the following structure:
FirstLocation (inherits Location)
- YSort
- Player
In the base Location scene I have two methods:
func add_player(player: Player):
get_node("YSort").add_child(player)
func remove_player() -> Player:
var player = get_node("YSort/Player")
get_node("YSort").remove_child(player)
return player
In GameWorld scene I store the possible locations inside a dictionary and the moving of the player happens inside change_location() function:
onready var _locations = {
Location.FOO: $CurrentLocation,
Location.BAR: load("res://locations/Bar.tscn").instance(),
}
onready var _current_location = $CurrentLocation
func change_location(location: int):
var player = _current_location.remove_player()
remove_child(_current_location)
_current_location = _locations[location]
add_child(_current_location)
_current_location.add_player(player)
The switching of the location works
The moving of the player also works in case the player is plain Node2D.
But when Player is KinematicBody2D then the game simply crashes, giving me no hint as to what's causing the problem.
The code works without crashing when I comment out the last line:
_current_location.add_player(player)
...but of course then the player simply doesn't get added to the other scene.
I verified that the player does get removed from the scene.
I tested with a dummy scene (which only contains KinematicBody2D as root node and a simple Sprite as a single child) instead of my actual more complex Player scene to make sure it's not related to any other code I might have in my Player scene. Node2D as root works, KinematicBody2D crashes. Must have been a fluke. Tested again and now both work, so there must be something different in my Player object.
I tried adding the Player node as a direct child of Location node (not having a YSort node in the middle) - nope, still crashes.
I tried setting the position/global_position of player before/after adding it to new scene - no difference.
I'm able to create new Player scene instance and add it to new location.
What might it be in KinematicBody2D that prevents me from moving it from scene to scene?
Found a solution, but I don't know why it works.
I was performing the location change as a response to Area2D.body_entered signal. I triggered my own signal "location_change" and then called the change_location() function in another part of the code in response to it.
Adding a tiny timeout (0.00000001 seconds) before doing the location change solved the issue. However I have no idea why, and I'm pretty sure adding timeouts is not a proper way to solve this problem.
I'm having trouble visualizing the situation. However, given that the problem happens when removing and adding a physics body, and that "body_entered" was involved, and that the solution you found was adding a time out…
Sounds like the issue was removing the physics body while Godot was still resolving physics response. And then the solution was to wait until the next frame.
You could wait until the next graphics frame with this:
yield(get_tree(), "idle_frame")
Or until the next physics frame with this:
yield(get_tree(), "physics_frame")
Which would be better than some arbitrary small timeout.
Alternatively, you could also make the signal connection deferred.
If you are connecting from the UI, there will be an "advanced" toggle in the "Connect a Signal to a Method" dialog. Enabling "advanced" toggle will reveal some extra including making the connection deferred.
If you are connecting form code, you can accomplish the same thing by passing the CONNECT_DEFERRED flag.
I have created a base scene that I intend to use for all human characters of my game. I am using an AnimatedSprite where I defined different animations for the different positions of the character, all using a texture that contains all the frames.
This works for a specific character, but now I would like to create other characters. Since I am using a character generator, all the sprite sheets are basically the same, but with different clothes, accessories, etc. I would like to avoid replicating the animation definitions for the other characters. I could achieve that by setting a different texture on each instance of the scene, but I can't find a way to do it.
If I edit the tscn file and set a different image, it does what I want.
I tried updating the atlas property of the animation frames, but doing that affects all instances of the scene:
func update_texture(value: Texture):
for animation in $AnimatedSprite.frames.animations:
for frame in animation.frames:
frame.atlas = value
I also tried cloning a SpriteFrames instance, by calling duplicate(0), updating it with the above code, then setting $AnimatedSprite.frames, but this also updates all instances of the scene.
What is the proper way to change the texture of a specific instance of AnimatedSprite?
I found a solution. The problem was that the duplicate method does not perform a deep clone, so I was having references to the same frame instances.
Here's my updated version:
func update_texture(texture: Texture):
var reference_frames: SpriteFrames = $AnimatedSprite.frames
var updated_frames = SpriteFrames.new()
for animation in reference_frames.get_animation_names():
if animation != "default":
updated_frames.add_animation(animation)
updated_frames.set_animation_speed(animation, reference_frames.get_animation_speed(animation))
updated_frames.set_animation_loop(animation, reference_frames.get_animation_loop(animation))
for i in reference_frames.get_frame_count(animation):
var updated_texture: AtlasTexture = reference_frames.get_frame(animation, i).duplicate()
updated_texture.atlas = texture
updated_frames.add_frame(animation, updated_texture)
updated_frames.remove_animation("default")
$AnimatedSprite.frames = updated_frames
I am adding a main menu to my game. The thing I am doing is adding them in a scene and then changing the scene to the game scene. However, my game has errors which belong to other scenes that do not have an instance in the existing scene. I get errors such as:
Invalid get index 'HasEntered' (on base: 'null instance').
My entire project is here: https://github.com/Ripple-Studios/Godot-Wild-Jam-36-Game-Ripple-Studios
I would appreciate if someone would help me.
Thanks,
I had a look at the linked code.
What is happening is that the practice of getting nodes of the parent has come back to bite you. I'm talking code that looks like this:
get_parent().get_node(...)
You have an scene (HospitalScene.tscn) instanced in your main scene (MainMenu.tscn), which has code similar to the shown above.
The particular error you refer to comes from code that looks like this:
func _on_Area2D_body_entered(body):
var HospitalPosition = get_parent().get_node("Hospital")
if HospitalPosition.HasEntered == true:
HospitalPosition.isInHospital = false
This code is firing at the start because the Area2D is overlapping an StaticBody.
The code is trying to get a sibling "Hospital" which does not exist in the scene tree. And thus HospitalPosition is null. And trying to access HospitalPosition.HasEntered when HospitalPosition is null results in the error you mention:
Invalid get index 'HasEntered' (on base: 'null instance').
The scene is trying to reach a node outside of itself. And there is no guarantee that the scene will be instanced where such node is available. Thus, in each and every case of get_parent().get_node(...) this could happen.
In fact, when running the game, I get four error that look like this (but with different paths):
E 0:00:01.494 get_node: (Node not found: "Hospital" (relative to "/root/CanvasLayer/ParentSprite/Control").)
<C++ Error> Condition "!node" is true. Returned: nullptr
<C++ Source> scene/main/node.cpp:1325 # get_node()
<Stack Trace> HospitalScene.gd:28 # _on_Area2D_body_entered()
You could use get_node_or_null instead of get_node and check for null.
You could also export NodePath variables instead of hard-coding the paths.
Better decoupling strategies than checking if instances are valid include:
Connect to the signal from outside the scene. It is a common pattern in Godot to call down the scene tree, and signal up the scene tree. See Node communication (the right way).
Connect all the signals through an Autoload (singleton). Which is another common pattern in Godot called a Signal Bus or Event Bus. See Best practices: Godot GDScript - Event Bus.
I am trying to create a topdown shooter with a player and a bullet on a separate scene. But whenever I run the game it says
Attempt to call function 'get_position' in base 'null instance' on a null instance.
BTW I am new to Godot.
The problem seems to be in this function:
const SPEED = 300
var bullet = preload("res://Mini-Scenes/Bullet.tscn")
func shoot():
var b = bullet.instance()
add_child(b)
b.set_position(position)
b.move_and_slide(Vector2(1, 0).rotated(rotation) * SPEED)
And I also don't think that I understand how instancing works,
so my questions are:
How does Instancing work?
What makes the above function fail?
Alright, in order:
Instancing is simple in principle. Godot takes the base Node of a scene and all its children, and copy-and-pastes them into memory. Then, when you add this Node as child to another in the scene, _ready is called, the Nodes begin to _process and _physics_process, as well as a few other things like receive events (as a Node must be within a SceneTree in order to interact with other nodes, and the most common way to add one to a tree is making it the child of another).
For more information, see the documentation on Instancing
The above function actually works flawlessly, I just created a new project in Godot 3.1.1 and duplicated your setup, no errors occur. The problem must be somewhere else in your code or your scene setup, and we'd need to see your full script and scene layout to determine the cause of the problem. If you update your question with that information, or shoot me a message on Discord (Mantissa#2558), I'll be able to fully answer your question.
I want the player to pickup objects in my game using the code below, but I am getting:
Error #1034: Type Coercion failed: cannot convert flixel::FlxSprite#51e1b69 to Player.
...
FlxG.overlap(weapons, players, onPickup)
}
private function onPickup(wep:Weapon, player:Player):Void
{
//access player function
}
I've initialized the players and weapons already as below, and added to the group
players= new FlxTypedGroup<Player>();
weapons= new FlxTypedGroup<Weapon>();
Weapon extends FlxSprite and Player extends FlxTypedGroup<FlxSprite>.
I'm using FlxTypedGroup because I want the player to have multiple sprites associated with it.
Please help so I can access the player class variables!
If I replace player:Player with player:FlxSprite there is no error, but then I can no longer access Player class functions.
I know this is probably a little bit late, but there are a few things you can try:
You could try using FlxSpriteGroup for Player instead of FlxTypedGroup. It may take some work to get it working the way you want.
Also, the reason why it's giving you an error, is because overlap and collide will (by default) drill down through your Groups until it comes to an actual object...
How to explain... If you have a FlxTypedGroup<Player> and your Player object extends FlxTypedGroup<PlayerPart> (if PlayerPart extends FlxSprite or something), when you do FlxG.overlap(weapons, players, onPickup), overlap is NOT going to pass the Player object, it's going to pass the PlayerPart object that overlapped - in fact, it's going to call onPickup once for EVERY PlayerPart object that overlaps a weapon - possibly the same one - this update.
You can use this behavior to your advantage, if you can figure it out - make your Player group contain several PlayerParts but set all of them to allowCollisions = NONE except for one which will be your hitbox, etc.
There's lots of things you can do, it's just figuring out the specifics. Good Luck!