#framework #utility #gamedev

macro node_tree_derive

Provides the NodeSys macro for the node_tree crate

3 releases

0.1.2 Apr 8, 2024
0.1.1 Apr 8, 2024
0.1.0 Apr 8, 2024

#1163 in #utility

Used in node_tree




Crates.io License Crates.io Version Documentation

NodeTree is a framework to create large scalable programs and games through a tree of processes. Each process is fully autonomous and is capable of storing its own state or data, and communicating with other processes. These processes are known as Nodes.

This crate is in early development. Beware of possible bugs or safety violations.
The specific nightly version this crate uses is v1.78.

Getting Started!

Simply either run cargo add node_tree at the terminal directed towards the directory of your project, or add node_tree = X.X to your cargo.toml file.

To begin creating a program in Rust that utilizes a NodeTree, we must first create a root Node. In order to reduce boilerplate, we will use the included NodeSys derive macro to implement the required Dynamic and NodeAbstract traits. We will then implement the Node trait ourselves.

#![feature(arbitrary_self_types)]   // Required for now.
use node_tree::prelude::*;

#[derive(Debug, Clone, NodeSys)]
pub struct NodeA {
    base: Rc<NodeBase>   // Required for Nodes.

// To make things simple, it is advised to have most node constructors return the node
// instance wrapped inside of this crate's `Hp<T>` pointer.
impl NodeA {
    fn new(name: String) -> Hp<Self> {
        Hp::new(NodeA { base: NodeBase::new(name) })

// Example implementation of the Node trait with custom behaviours.
impl Node for NodeA {

    /// Run once the Node is added to the NodeTree.
    fn ready(self: Hp<Self>) -> () {

        // To show off how you could add children nodes.
        if self.depth() < 3 {
            self.add_child(NodeA::new(format!("{}_Node", self.depth() + 1)));
            self.add_child(NodeA::new(format!("{}_Node", self.depth() + 1)));
            self.add_child(NodeA::new(format!("{}_Node", self.depth() + 1)));

        if self.is_root() {
            println!("{:#?}", self.children());

    /// Run once per frame. Provides a delta value in seconds between frames.
    fn process(self: Hp<Self>, delta: f32) -> () {

        // Example of using the delta value to calculate the current framerate.
        println!("{} | {}", self.name(), 1f32 / delta);

        // Using the NodePath, you can reference other nodes in the NodeTree from this node.
        if self.is_root() {
            match self.get_node(NodePath::from_str("1_Node/2_Node1/3_Node2")) {
                Some(node) => println!("{:?}", node),
                None       => ()

        // Nodes can be destroyed. When destroyed, their references from the NodeTree are cleaned up as well.
        // If the root node is destroyed, then the program automatically exits. (There are other ways to
        // terminate the program such as the queue_termination() function on the NodeTree instance).
        if self.children().is_empty() {
            self.free();   // We test the progressive destruction of nodes from the tip of the tree
                           // to the base.

    /// Runs once a Node is removed from the NodeTree, whether that is from the program itself terminating or not.
    fn terminal(self: Hp<Self>) -> () {}   // We do not do anything here for this example.

    /// Returns this node's process mode.
    /// Each process mode controls how the process() function behaves when the NodeTree is paused or not.
    /// (The NodeTree can be paused or unpaused with the pause() or unpause() functions respectively.)
    fn process_mode(self: Hp<Self>) -> ProcessMode {
        ProcessMode::Inherit    // We will return the default value, which inherits the behaviour from
                                // the parent node.

Finally, in order to activate our NodeTree, we must instance the root Node and feed it into the NodeTree constructor.

// ...previous implementations

fn main() -> () {

    // Create the tree.
    let root: Hp<NodeA>    = NodeA::new("Root".to_string());
    let tree: Hp<NodeTree> = NodeTree::new(root);

    // Begin operations on the tree.
    tree.process();   // This will run an indefinite loop until the program exits.


  • 🏗️ An easy abstraction framework for different processes to communicate and interact with each other in a scalable manner. Inspired by Godot!
  • ⏯️ The ability to pause() and unpause() the NodeTree, and fine tune individual Node behaviours for when a tree is paused/unpaused.
  • 📡 Various methods to communicate with other nodes, such as owner(), parent(), get_child(), children(), and get_node().
  • 🔗 An abstracted smart pointer known as Hp<T> which clones implicitly to reduce syntax noise and allows for low boilerplate.
  • 👪 The ability to manage nodes with add_child() and remove_child().
  • 🌲 Allows for the direct referencing of the NodeTree through a node's root() function.
  • 📚 TODO: A caching system hosted on the NodeTree to act as a safe interface to ensure the Hp<T> soundness, and increase performance!
  • 📜 TODO: Includes a method to save and handle individual node scenes, such as the handy visual macro Scene!.


~34K SLoC