gdrust_export_node_path_macro

Reduces boilerplate code when acquiring references through NodePath. Usage consists of (full example on a few paragraphs bellow):

• Replacing #[derive(NativeClass, Default)] #[inherit(Node)] with #[extends(Node)]
• Removing the NodePath fields marked with #[property]
• Placing #[export_path] behind the fields you wish to acquire through NodePath
• Removing your implementation of fn new(&mut self, _owner: &Node)
• Manually call self.grab_nodes_by_path(_owner); on your _ready() declaration

The #[extends] attribute macro:

• Replaces itself with #[derive(NativeClass)] #[inherit(Node)]
• Then, for each field marked with #[export_path]:
  • Declares another field of similar name but with a path_ prefix and NodePath as type, as well as a regular #[property] attribute. (Vec<Ref<Node>> uses a Vec<NodePath> type instead)
  • Example input/output: #[export_path] node: Option<Ref<Node>> / #[property] path_node: NodePath, node: Option<Ref<Node>>,
• Declares a impl block with two functions:
  • fn grab_nodes_by_path(&mut self, _owner: &Node) { // searches for all the nodes/instances from the NodePath fields generated, assigning each to their original field in self }
  • fn new(_owner: &Node) -> Self { Self::default() }

Supports exporting:

• Option<Ref<T>> where T is a Godot's built-in type that inherits Node (such as: Node2D, Control, ProgressBar, KinematicBody, ...)
• Vec<Ref<T>> where T is a Godot's built-in type that inherits Node
• Option<Instance<T>> where T is a custom native script defined by you, as long as the script inherits a Godot's built-in type that inherits Node
• Vec<Instance<T>> where T is a custom native script defined by you, as long as the script inherits a Godot's built-in type that inherits Node

PS 1: Note that Vec<Ref<T>>/Vec<Instance<T>> uses Ref<T>/Instance<T> directly instead of Option<Ref<T>>/Option<Instance<T>>

PS 2: Not related to this crate, but to gdnative-rust itself: In the editor, Vec<NodePath> will be shown as an array of Variant, you have to click on each element of the array, chose NodePath, then you'll be able to drag nodes in.

The base of the implementation was taken from gdrust.

Usage

Replace

#[derive(NativeClass)]
#[inherit(Node)]
struct MyGodotScript {
    #[property] path_exported_node: NodePath,
    exported_node: Option<Ref<Node>>,

    #[property] path_exported_instance: NodePath,
    exported_instance: Option<Instance<NativeScriptTest>>,

    #[property] paths_exported_nodes: Vec<NodePath>,
    vec_nodes: Vec<Ref<Node>>,

    #[property] paths_exported_instances: Vec<NodePath>,
    vec_instances: Vec<Instance<NativeScriptTest>>,
}

impl MyGodotScript {
    fn new(_owner: &Node) -> Self {
        return Self {
            path_exported_node: NodePath::default(),
            exported_node: None,

            path_exported_instance: NodePath::default(),
            exported_instance: None,

            paths_exported_nodes: Vec::new(),
            vec_nodes: Vec::new(),

            paths_exported_instances: Vec::new(),
            vec_instances: Vec::new(),
        };
    }
}

#[methods]
impl MyGodotScript {
    #[method]
    fn _ready(&mut self, #[base] _owner: &Node) {
        self.exported_node = Some(unsafe {_owner.get_node_as::<Node>(self.path_exported_node.new_ref()).unwrap().assume_shared()});
        self.exported_instance = Some(unsafe {_owner.get_node_as_instance::<NativeScriptTest>(self.path_exported_instance.new_ref()).unwrap().claim()});

        for path in self.paths_exported_nodes.iter() {
            self.vec_nodes.push(unsafe { _owner.get_node_as::<Node>(path.new_ref()).unwrap().assume_shared()});
        }

        for path in self.paths_exported_instances.iter() {
            self.vec_instances.push(unsafe { _owner.get_node_as_instance::<NativeScriptTest>(path.new_ref()).unwrap().claim()});
        }
    }
}

#[derive(NativeClass)]
#[inherit(Node)]
pub struct NativeScriptTest { }

impl NativeScriptTest {
    fn new(_owner: &Node) -> Self {
        return Self {};
    }
}

With

#[extends(Node)] // you can replace Node with any other Godot built-in node type
struct MyGodotScript {
    #[export_path] exported_node: Option<Ref<Node>>,                        // you can replace Node with any other Godot built-in node type
    #[export_path] exported_instance: Option<Instance<NativeScriptTest>>,   // replace NativeScriptTest with your own type
    #[export_path] vec_nodes: Vec<Ref<Node>>,                               // you can replace Node with any other Godot built-in node type
    #[export_path] vec_instances: Vec<Instance<NativeScriptTest>>,          // replace NativeScriptTest with your own type
}

#[methods]
impl MyGodotScript {
    #[method]
    fn _ready(&mut self, #[base] _owner: &Node) { // replace Node with the extended type
        self.grab_nodes_by_path(_owner);  // you must call this manually, it replaces your old _ready() call
    }
}

#[extends(Node)]
pub struct NativeScriptTest { }

Which expands to (manually formatted for readability)

#[derive(gdnative::prelude::NativeClass, Default)]
#[inherit(Node)]
struct MyGodotScript {
    #[property] path_vec_instances: Vec<gdnative::prelude::NodePath>,
    #[property] path_vec_nodes    : Vec<gdnative::prelude::NodePath>,
    #[property] path_exported_instance: gdnative::prelude::NodePath,
    #[property] path_exported_node    : gdnative::prelude::NodePath,
    exported_node: Option<Ref<Node>>,
    exported_instance: Option<Instance<NativeScriptTest>>,
    vec_nodes: Vec<Ref<Node>>,
    vec_instances: Vec<Instance<NativeScriptTest>>,
}

impl MyGodotScript {
    fn new(_owner: &Node) -> Self { Self::default() }

    fn grab_nodes_by_path(&mut self, owner: &Node) {
        self.exported_node = Some(unsafe { owner.get_node_as::<Node>(self.path_exported_node.new_ref()).unwrap().assume_shared() });
        self.exported_instance = Some(unsafe { owner.get_node_as_instance::<NativeScriptTest>(self.path_exported_instance.new_ref()).unwrap().claim() });

        for path in self.path_vec_nodes.iter() {
            self.vec_nodes.push(unsafe { owner.get_node_as::<Node>(path.new_ref()).unwrap().assume_shared() });
        }

        for path in self.path_vec_instances.iter() {
            self.vec_instances.push(unsafe { owner.get_node_as_instance::<NativeScriptTest>(path.new_ref()).unwrap().claim() });
        }
    }
}

Misc / Limitations

• You may still freely use the other gdnative attributes like #[register_with] #[no_constructor] #[user_data] #[property]. Just make sure to always place them bellow #[extends], except #[property] which still goes behind fields.
• grab_nodes_by_path(&mut self, owner: &Node) will panic if it fails to validate any of the exported paths.
• You cannot define your own Self::new().
• _owner in grab_nodes_by_path(&mut self, owner: &Node) uses hardcoded &, so you cannot declare owner in _ready(&mut self, #[base] _owner: &Node) as owner: TRef<Node>.