Signal

Installation

Pesde

pesde add molyidev/signal

Wally

Signal = "molyidev/signal@^1.0.1"

Why use Signal?

• Fully typed: Designed to work with the new Luau type solver.
• Priority: Includes a PrioritySignal variant, allowing you to control the exact execution order of your connections.
• Performance: Uses a Doubly Linked List for O(1) removal and LIFO cleanup structure.
• GC Friendly: Designed to have minimal memory allocation.

Usage

Basics

local Signal = require(path.to.Signal)

-- Create a standard signal
local signal = Signal.new()

-- Connect to the signal
local connection = signal:Connect(function(msg)
    print("Received:", msg)
end)

-- Fire the signal
signal:Fire("Hello World!") 

-- Clean up
connection:Disconnect()

Priority Signal

local Signal = require(path.to.Signal)

local prioritySignal = Signal.newPriority()

-- Priority 10 (Runs second)
prioritySignal:ConnectPriority(10, function()
    print("Second")
end)

-- Priority 0 (Runs first)
prioritySignal:ConnectPriority(0, function()
    print("First")
end)

prioritySignal:Fire()
-- Output:
-- First
-- Second

Type Checking

local Signal = require(path.to.Signal)

-- Define a signal that accepts a number and a string
local signal = Signal.new() :: Signal.Signal<number, string>

signal:Connect(function(num, text)
    -- 'num' is inferred as number
    -- 'text' is inferred as string
    print(num, text)
end)

signal:Fire(10, "str") -- Valid
signal:Fire("str", 10) -- Type Error

Synchronous Firing

By default, Fire runs listeners in separate threads. Use FireSync to run them immediately and yield until they finish.

signal:FireSync("Yields current thread until all listeners finish")

Bound Args

You can pass arguments to :Connect() that will be bound to that specific connection. These arguments are passed to your callback first, followed by any arguments passed to :Fire().

local Signal = require(path.to.Signal)

local signal = Signal.new()

-- Bind '1000' and '"context"' to this specific connection
signal:Connect(function(boundNum, boundStr, firedStr)
    print(boundNum, boundStr, firedStr)
end, 1000, "context")

-- This connection has no bound arguments
signal:Connect(function(firedStr)
    print(firedStr)
end)

signal:Fire("strExample")

-- Output:
-- 1000 context strExample
-- strExample

API

Static Signal

Method	Description
.new()	Creates a new standard Signal.
.newPriority()	Creates a new PrioritySignal.
.IsSignal(obj)	Returns true if obj is a Signal or PrioritySignal.
.IsConnection(obj)	Returns true if obj is a Connection.

Signal

Method	Description
:Connect(fn, ...)	Connects a function to the signal. Returns a Connection.
:Once(fn, ...)	Connects a function that runs only once, then disconnects. Returns a Connection.
:Wait()	Yields the current thread until the signal is fired. Returns the arguments fired.
:Fire(...)	Fires the signal. Listeners run in separate threads.
:FireSync(...)	Fires the signal synchronously.
:DisconnectAll()	Disconnects all connections.
:Destroy()	Disconnects all connections and leaves the signal unusable.

PrioritySignal (Inherits Signal)

Method	Description
:ConnectPriority(priority, fn, ...)	Connects with a specific priority. Lower executes first. Returns a Connection.
:OncePriority(priority, fn, ...)	Connects once with a specific priority. Returns a Connection.
:WaitPriority(priority)	Yields until fired. The temporary connection uses the given priority. Returns the arguments fired.

Note: PrioritySignal also has the standard methods (Connect, Once, etc.), which default to priority 0.

Connection

Property/Method	Description
.Connected	Boolean. true if the connection is active.
:Disconnect()	Disconnects the listener from the signal.
:Reconnect()	Re-activates a disconnected listener (maintains original priority).

Benchmarks

Benchmarks are located in the ./public/ directory.

Speed - 5K Iterations

• Signal and LemonSignal have the same raw speed performance.
• Signal is faster than FastSignal.
• Since LemonSignal and FastSignal both outperform GoodSignal, Signal is consequently faster than GoodSignal.

Memory - 10K Iterations

The following table compares memory usage across different operations. Signal is designed to be GC-friendly with 0 allocations during firing.

Operation	Signal	LemonSignal	FastSignal
New	782 KB	782 KB	1.07 MB
Connect	2.90 MB	3.36 MB	3.97 MB
Fire	0 KB	0 KB	11.14 MB
Fire (Bound Args)	0 KB	938 KB	N/A
FireSync	0 KB	N/A	N/A
FireSync (Bound Args)	0 KB	N/A	N/A

• vs LemonSignal:

  • Uses ~14% less memory in Connect.
  • Uses 100% less memory in Fire with Bound Args (0 KB vs 938 KB).

• vs FastSignal:

  • Uses ~27% less memory in new.
  • Uses ~27% less memory in Connect.
  • Uses 100% less memory in Fire (0 KB vs 11.14 MB).

Inspiration

Signal takes inspiration from both LemonSignal and FastSignal. These libraries are fantastic. If you do not want to use Signal and would prefer another option, I highly recommend either of them. However, if I had to choose between the two, I would recommend LemonSignal.