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fix(range): ensure RangeStream is only listened to once #694

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Oct 12, 2022
Merged

fix(range): ensure RangeStream is only listened to once #694

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42 changes: 15 additions & 27 deletions lib/src/streams/range.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ import 'dart:async';
///
/// RangeStream(3, 1).listen((i) => print(i)); // Prints 3, 2, 1
class RangeStream extends Stream<int> {
var _isListened = false;
final Stream<int> _stream;

/// Constructs a [Stream] which emits all integer values that exist
Expand All @@ -18,36 +19,23 @@ class RangeStream extends Stream<int> {

@override
StreamSubscription<int> listen(void Function(int event)? onData,
{Function? onError, void Function()? onDone, bool? cancelOnError}) =>
_stream.listen(onData,
onError: onError, onDone: onDone, cancelOnError: cancelOnError);
{Function? onError, void Function()? onDone, bool? cancelOnError}) {
if (_isListened) {
throw StateError('Stream has already been listened to.');
}
_isListened = true;

return _stream.listen(onData,
onError: onError, onDone: onDone, cancelOnError: cancelOnError);
}

static Stream<int> _buildStream(int startInclusive, int endInclusive) {
final controller = StreamController<int>(sync: true);
StreamSubscription<int>? subscription;

controller.onListen = () {
final length = (endInclusive - startInclusive).abs() + 1;
int nextValue(int index) => startInclusive > endInclusive
? startInclusive - index
: startInclusive + index;

subscription =
Stream.fromIterable(Iterable.generate(length, nextValue)).listen(
controller.add,
onError: controller.addError,
onDone: controller.close,
);
final length = (endInclusive - startInclusive).abs() + 1;

controller.onPause = subscription!.pause;
controller.onResume = subscription!.resume;
};
controller.onCancel = () {
final future = subscription?.cancel();
subscription = null;
return future;
};
int nextValue(int index) => startInclusive > endInclusive
? startInclusive - index
: startInclusive + index;

return controller.stream;
return Stream.fromIterable(Iterable.generate(length, nextValue));
}
}