`append`

Yields all values of the source, then one extra value at the end.

Iterable<A> append<A>(A a, Iterable<A> iterable) FxAsyncIterable<A> appendAsync<A>(FutureOr<A> a, FxAsyncIterable<A> iterable) Fx<T> Fx.append(T a) // chain FxAsync<T> FxAsync.append(FutureOr<T> a)

Lecture

append is the simplest way to tack a single trailing value onto a lazy sequence without materializing anything: it just yields through the whole source and then yields a once the source is exhausted. Because the source is only consumed when pulled, this works fine even when the source is expensive to compute — the extra value is truly the last thing produced.

On the async side, a itself may be a Future — appendAsync awaits it only once the upstream is done, so a slow "closing" value doesn't hold anything up early.

Demo 1 · Basics

Demo 2 · Async, with a future value

Try it yourself

Exercise: append 'cool' to the end of the steps.

Related: prepend — add a value at the front instead · concat — join two full iterables · reverse