combine-latest

Combines two streams into a new stream which yields tuples with the latest values from each input stream. Inspired by Rx's combineLatest.

use async_stream::stream;
use combine_latest::combine_latest;

fn combine_weather_data_streams(
    temperature: impl Stream<i32>,
    weather_notes: impl Stream<String>,
) -> Stream<String> {
    stream! {
        for await (t, n) in combine_latest(temperature, weather_notes) {
            yield format!("Temperature {t}°, note: {n}");
        }
    }
}

combine_latest won't yield its first tuple until both input streams have yielded a value. If you need to get items as soon as the first is available, there is a combine_latest_optional function that yields (Option, Option) tuples.

As values come in over time on the temperature and weather_notes streams, combine_latest and combine_latest_optional will yield values like so:

Since the same input value might be returned several times in the output stream, the items that the input streams yield must implement Clone.