Once (Flowgraph Node)

Overview

• Node Name: Once
• Category: logic
• Behaviour: {once = true}
• File: extensions/flowgraph/nodes/logic/once.lua

Only lets flow through a single time. After firing once, blocks all subsequent flow until reset.

Pin Schema

Input Pins

Output Pins

Behavior

• init(mgr, ...) - Sets ready to true.
• work(args) - If reset is triggered, re-arms the node. Otherwise, if ready and flow is active, outputs flow once and sets ready to false. All subsequent calls output false until reset.
• _executionStopped() - Re-arms the node (sets ready to true).

How It Works

The node acts as a one-shot gate. On the first frame that flow arrives, it passes through and the gate closes. The gate stays closed until either:

1. The reset impulse pin fires
2. Execution stops and restarts

This is commonly used to trigger initialization logic or one-time events that should not repeat.

Example Usage

-- Trigger a welcome message only once:
-- flow → [Once] → [Show Message "Welcome!"]
-- Even if flow continues, the message only shows once

-- Reset after a level change:
-- Connect level-changed event to reset pin
-- The Once node re-arms and can fire again

See Also

• And (Flowgraph Node) - Related reference
• Boolean Expression (Flowgraph Node) - Related reference
• Branch (Flowgraph Node) - Related reference
• FlowGraph Guide - Guide