ReactiveSignal

A simple addon to make UI / Game Logic reactive in Godot 4.x (GDScript).

Inspired by the signal/reactive systems in modern frontend frameworks (like React, Vue, and SolidJS).

✨ Features

• True Reactivity: No need to manually connect or emit signals. Simply access data inside use_effect, and the dependency tracking is automatically handled.
• Lightweight & Efficient: Built on top of RefCounted for automatic memory management, preventing memory leaks.
• Zero Coupling: Keeps your data layer completely decoupled from the view layer, significantly reducing boilerplate code like connect() and emit_signal().

🚀 Quick Start

1. Basic Usage (Data Responsiveness)

Use use_effect to track and respond to data changes automatically:

extends Node

func _ready() -> void:
    # 1. Create a reactive signal
    var score = ReactiveSignal.new(0)

    # 2. Define a side effect (automatically runs whenever score.value changes)
    ReactiveSignal.use_effect(func():
        print("Current Score: ", score.value)
    ) # Prints: "Current Score: 0"

    # 3. Modify the data, which automatically triggers updates
    score.value = 10  # Prints: "Current Score: 10"
    score.value = 10  # Value unchanged, won't trigger
    score.value = 25  # Prints: "Current Score: 25"

2. Auto-Updating UI Components

Perfect for scenarios where multiple UI elements share and display the same state:

extends Control

@onready var label_1: Label = $Label1
@onready var label_2: Label = $Label2

# Create a global or local state
var player_hp = ReactiveSignal.new(100)

func _ready() -> void:
    # Keep multiple UI elements in perfect sync automatically
    ReactiveSignal.use_effect(func():
        label_1.text = "HP: " + str(player_hp.value)
        label_2.text = "Health: " + str(player_hp.value) + "%"
    )

func _on_damage_taken(amount: int) -> void:
    player_hp.value -= amount # UI updates automatically! No need to manually assign Label.text

3. Computed Signal

Evaluating other signals to a new signal. General speaking, if a signal C is computed from signals A+B then any changes from A or B will automatically updates signal C.

Example:

var first_name = ReactiveSignal.new('')
var last_name = ReactiveSignal.new('')
var full_name = ReactiveSignal.computed(func(): 
    return first_name.value + ' ' + last_name.value
)
var intro = ReactiveSignal.computed(func():
    return 'My name is: %s' % full_name.value)

func _ready() -> void:
    # Bind the ui native event signals to our ReactiveSignals
    first_name_input.text_changed.connect(func(new_text): first_name.value = new_text)
    last_name_input.text_changed.connect(func(new_text): last_name.value = new_text)

    # Runs on intro value changed
    ReactiveSignal.use_effect(func():
        intro_label.text = intro.value
    )

    # Runs on first_name or last_name value changed
    ReactiveSignal.use_effect(func():
        var deps = [first_name.value, last_name.value]
        if not deps[0]:
            warning_label.text = 'First name should not be empty'
        elif not deps[1]:
            warning_label.text = 'Last name should not be empty'
        else:
            warning_label.text = ''
    )

🛠️ API Reference

ReactiveSignal

• static func use_effect(effect: Callable) -> void Executes the provided closure function and automatically collects any ReactiveSignal instances accessed within it. When the value of those instances changes, the effect is automatically re-invoked.
• func _init(initial_value) -> void Constructor that initializes the signal with its starting value.
• func clear_effects() -> void Manually clears all tracking side effects bound to this signal instance (useful for manual cleanup or destruction).

• var value Get: Returns the current value. If called within a use_effect closure, it automatically registers the effect as a dependency. Set: Assigns a new value. If the new value differs from the current one, it dispatches and re-runs all dependent effects. It also automatically cleans up any stale or invalid (freed) Callables during the dispatch process.

📦 Installation

1. Download or clone this repository, and copy the addons/ReactiveSignal folder into your Godot project's root directory.
2. Open the Godot Editor, navigate to Project -> Project Settings -> Plugins.
3. Locate ReactiveSignal and check the Enable box.

📄 License

This project is open-source and licensed under the MIT License.