Intervals

Periodic callbacks that run on a fixed schedule.

let ticks = state!(cx, || 0u64);

interval!(cx, Duration::from_secs(1), with!(ticks => move || {
    ticks.update(|n| *n += 1);
}));

View::text(format!("Ticks: {}", ticks.get()))

Run with: cargo run -p telex-tui --example 34_channels_and_intervals

What is interval!?

interval! sets up a repeating timer that fires a callback on the main thread. Under the hood, it spawns a background thread with a WakingSender channel — the timer thread sends a wake-up signal, and the callback runs during the next frame.

interval!(cx, duration, callback);

duration — A std::time::Duration for the interval period
callback — A closure that runs on the main thread each frame the timer fires

Common uses

Polling

let data = state!(cx, || None);

interval!(cx, Duration::from_secs(5), with!(data => move || {
    // Runs every 5 seconds on the main thread
    if let Ok(fresh) = quick_fetch() {
        data.set(Some(fresh));
    }
}));

Animation

let frame = state!(cx, || 0usize);
let sprites = ["| ", "/ ", "- ", "\\ "];

interval!(cx, Duration::from_millis(100), with!(frame => move || {
    frame.update(|f| *f = (*f + 1) % 4);
}));

View::text(sprites[frame.get()])

Blinking cursor

let visible = state!(cx, || true);

interval!(cx, Duration::from_millis(500), with!(visible => move || {
    visible.update(|v| *v = !*v);
}));

Interval vs stream

Use interval! when:

You need periodic side effects (polling, animation)
The callback is simple and runs on the main thread
You want the timer to fire even if no data changed

Use stream! when:

You need to yield data values over time
The work runs in a background thread
You want loading/completion tracking with .is_loading()

Tips

Main thread execution — The callback runs on the main thread during the render cycle. Keep it fast — don't do heavy computation or blocking I/O in the callback.

Order-independent — Like all macros, interval! is keyed by call site. Safe in conditionals and loops.

Automatic cleanup — The timer thread stops when the component unmounts.

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