Why use a custom duplicate() function over Godot’s?#

Recently, I ran into an error when trying to duplicate a custom resource that had subresources attatched to it. Neither the subresources or normal varibles would duplicate, it would just created a new file but didn’t copy any of the values. After some googling, I found this github issue from Godot 3. After some scrolling I saw a response about how to make your own duplicate function to fix this issue. I’ll be breaking down the code and how it works here!

Tutorial#

• We’ll need a single script, which I called CustomDuplicate
• We just need a single function, which you can name whatever you’d like, I’ve called mine deep_clone()
• Our function will take in an Object (which is what we’ll want to clone) and return an Object (the final copy)
• First, we use godots built-in duplicate() function
• Then, we’ll loop through all the properties in the clone, and set them equal to their values in the original
  • This overrides every variable, making sure that none get missed from the original duplicate() call
• We might be done here in some cases, but in the case we’re duplcating a node with children, we’ll copy those too
• After making sure the _object is a Node, we’ll remove all the children on the clone
• Once we’ve remove all the children, we’ll use an assert to make sure they did in fact all get removed
• Lastly, we’ll get all the children from the object and call deep_clone (to make sure they get copied properly too) on all of them before adding them as a child to our _object
• And of course return our clone at the end

## Code from https://github.com/godotengine/godot/issues/37222
extends Node
class_name CustomDuplicate

static func deep_clone(_object_ : Object) -> Object:
	## Create a shallow copy
	var clone : Object = _object_.duplicate()

	## get_property_list() returns an array of all the properties
	## loop through all the properties and store their values
	## makes sure any data the duplicate() misses gets copied over
	for property in _object_.get_property_list():
		var propertyName = property["name"]
		clone.set(propertyName, _object_.get(propertyName))

	## properly duplicate all children nodes 
	if _object_ is Node:
		## delete any previously cloned children
		for child in clone.get_children():
			clone.remove_child(child)
			child.free()

		## make sure all children were removed
		assert(clone.get_child_count() == 0)

		## go through each child and deep clone them
		for child in _object_.get_children():
			clone.add_child(deep_clone(child))

	return clone

Why is it a singleton instead of an autoload?#

An autoload will create a node for it inside the scene tree, but we have no need for a node inside the tree, we just need access to the function so using a static function is enough and aviods unecessary nodes.

And that’s it! Since this is a static function, we can call it anywhere in our codebase like an autoload by doing var duplicateObject : Object = CustomDuplicate.deep_clone(objectHere).

References#

Solution from Github Issue