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import { Observable } from '../Observable';
import { SchedulerLike } from '../types';
import { iterator as Symbol_iterator } from '../symbol/iterator';
import { isFunction } from '../util/isFunction';
import { executeSchedule } from '../util/executeSchedule';
/**
* Used in {@link scheduled} to create an observable from an Iterable.
* @param input The iterable to create an observable from
* @param scheduler The scheduler to use
*/
export function scheduleIterable<T>(input: Iterable<T>, scheduler: SchedulerLike) {
return new Observable<T>((subscriber) => {
let iterator: Iterator<T, T>;
// Schedule the initial creation of the iterator from
// the iterable. This is so the code in the iterable is
// not called until the scheduled job fires.
executeSchedule(subscriber, scheduler, () => {
// Create the iterator.
iterator = (input as any)[Symbol_iterator]();
executeSchedule(
subscriber,
scheduler,
() => {
let value: T;
let done: boolean | undefined;
try {
// Pull the value out of the iterator
({ value, done } = iterator.next());
} catch (err) {
// We got an error while pulling from the iterator
subscriber.error(err);
return;
}
if (done) {
// If it is "done" we just complete. This mimics the
// behavior of JavaScript's `for..of` consumption of
// iterables, which will not emit the value from an iterator
// result of `{ done: true: value: 'here' }`.
subscriber.complete();
} else {
// The iterable is not done, emit the value.
subscriber.next(value);
}
},
0,
true
);
});
// During finalization, if we see this iterator has a `return` method,
// then we know it is a Generator, and not just an Iterator. So we call
// the `return()` function. This will ensure that any `finally { }` blocks
// inside of the generator we can hit will be hit properly.
return () => isFunction(iterator?.return) && iterator.return();
});
}
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