delayed

README

Delayed Transitions

This example models a state with a built-in timeout. The machine enters a waiting state and starts a 100ms timer. If no event arrives before the timer fires, the machine automatically transitions to timeout. But if a USER_ACTION event shows up in time, the machine moves to other_state and the pending timer is cancelled — no cleanup code required.

State Diagram

---
title: Timeout
config:
    theme: default
    maxTextSize: 50000
    maxEdges: 500
    fontSize: 16
---
stateDiagram-v2
    state "other_state" as other_state
    state "timeout" as timeout
    state "waiting" as waiting
	[*] --> waiting
	waiting --> other_state: USER_ACTION
	waiting --> timeout: after 100ms

SCXML

<?xml version="1.0" encoding="UTF-8"?>
<scxml xmlns="http://www.w3.org/2005/07/scxml" version="1.0" name="timeout_demo" initial="waiting">
  <state id="other_state"></state>
  <state id="timeout"></state>
  <state id="waiting">
    <onentry>
      <send event="_delay.waiting" delay="100ms"></send>
    </onentry>
    <transition event="USER_ACTION" target="other_state"></transition>
    <transition event="_delay.waiting" target="timeout"></transition>
  </state>
</scxml>

What Happens

Case 1 — Timeout fires. The machine enters waiting and the 100ms timer starts. No events arrive. After 100ms the delayed transition fires and the machine moves to timeout.

Case 2 — Escaped before timeout. The machine enters waiting and the same 100ms timer starts, but this time a USER_ACTION event is sent at roughly 20ms. The machine exits waiting and transitions to other_state. Because the state was exited, the pending timer is automatically cancelled and timeout never fires.

When To Use This

• Session timeouts — idle too long and the user is logged out.
• Debounced input — wait for typing to stop before running validation.
• Heartbeat monitors — no ping within N seconds means disconnected.

Output

--- Test Case 1: Reaching the Timeout ---
[waiting] State entered. Starting 100ms timer...
[timeout] The timer fired! Transitioned successfully.

--- Test Case 2: Escaping before Timeout ---
[waiting] State entered. Starting 100ms timer...
Action: Sending 'USER_ACTION' before 100ms is up...
[other_state] Left 'waiting' before timeout.

--- Conclusion ---
Delayed transitions handle complex time-based logic natively,
eliminating the need for manual time.Sleep() or timers.

Running

go run .