rxdart_ext

Author: Petrus Nguyễn Thái Học

Some extension methods and classes built on top of RxDart - RxDart extension.

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Supported Dart SDK version: >=2.12.0 <3.0.0

RxDart compatibility

rxdart	rxdart_ext
^0.27.2	0.1.2
^0.27.3	0.1.3 → 0.2.0
^0.27.4	0.2.1 → 0.2.2
^0.27.5	0.2.3 → 0.2.7

• For example: when using rxdart: ^0.27.4 → we can use rxdart_ext: ^v where v in 0.2.1 → 0.2.7 (i.e. all rows since ^0.27.4 row in the above table).

• But in some cases there is any conflict between rxdart version and rxdart_ext version, you must use stricter version, eg. rxdart: ^0.27.4 → rxdart_ext: ^v where v in 0.2.1 → 0.2.2 (same row in the above table)

• The latest version of rxdart_ext always works fine with the latest version of rxdart.

API - Documentation

1. Single

A Stream which emits single event, either data or error, and then close with a done-event.

Success case: ------------(*)|------
                         data done

Failure case: ------------(x)|------
                        error done

NOTE: Single extends Stream, so all operators and transformers for Stream are available for Single as well.

Single is suitable for one-shot operations (likes Future but lazy - executes when listening), eg. making API request, reading local storage, ...

import 'package:http/http.dart' as http;

Single<User> fetchUser(String id) {
  return Single.fromCallable(() => http.get(Uri.parse('$baseUrl/users/$id')))
      .flatMapSingle((res) => res.statusCode == HttpStatus.ok
          ? Single.value(res.body)
          : Single.error(Exception('Cannot fetch user with id=$id')))
      .map((body) => User.fromJson(jsonEncode(body)));
}

• Create Single

  • Factory constructors.

    • Single.unsafeFromStream
    • Single.value
    • Single.error
    • Single.fromFuture
    • Single.fromCallable
    • Single.timer
    • Single.defer
    • Single.retry

  • Static methods provided by RxSingles class

    • RxSingles.zip2
    • RxSingles.forkJoin2 ..RxSingles.forkJoin9 and RxSingles.forkJoinList
    • RxSingles.using

  • Convert others to Single via extensions.

    • Stream.singleOrError
    • Future.asSingle
    • (FutureOr<T> Function()).asSingle

• Operators for Single (returns a Single instead of Stream)

  • flatMapSingle
  • flatMapEitherSingle
  • asyncExpandSingle
  • switchMapSingle
  • exhaustMapSingle
  • debug
  • delay
  • doOnCancel
  • doOnData
  • doOnError
  • doOnListen
  • onErrorReturn
  • onErrorReturnWith
  • onErrorResumeSingle
  • onErrorResumeNextSingle
  • mapTo
  • toEitherSingle
  • asVoid

2. Operators for Stream

• debug, collect
• distinctUniqueBy
• distinctBy
• doOn
• doneOnError
• flatMapBatches
• flatMapBatchesSingle
• ignoreErrors
• mapNotNull (moved to rxdart 0.27.4 as standard operator: mapNotNull)
• toSingleSubscription
• asVoid
• whereNotNull (moved to rxdart 0.27.4 as standard operator: whereNotNull)

3. StateStream

A Stream that provides synchronous access to the last emitted item, and two consecutive values are not equal. The equality between previous data event and current data event is determined by StateStream.equals. This Stream always has no error.

• Broadcast
  • StateSubject
  • StateConnectableStream
    • publishState
    • shareState
• Single-subscription
  • toStateStream

Example

Useful for Flutter BLoC pattern - StreamBuilder, expose broadcast state stream to UI, can synchronous access to the last emitted item, and distinct until changed

• Distinct: distinct until changed.
• Value: can synchronous access to the last emitted item.
• NotReplay: not replay the latest value.
• Connectable: broadcast stream - can be listened to multiple time.

                                Stream (dart:core)
                                   ^
                                   |
                                   |
            |--------------------------------------------|
            |                                            |
            |                                            |
        ValueStream (rxdart)                             |
            ^                                            |
            |                                            |
            |                                            |
    NotReplayValueStream (rxdart_ext)                    |
            ^                                    ConnectableStream (rxdart)
            |                                            ^
            |                                            |
       StateStream (rxdart_ext)                          |
            ^                                            |
            |                                            |
            |------------                     -----------|
                        |                     |
                        |                     |
                     StateConnectableStream (rxdart_ext)

class UiState { ... }

final Stream<UiState> state$ = ...;

final StateConnectableStream<UiState> state$ = state$.publishState(UiState.initial());
final connection = state$.connect();

StreamBuilder<UiState>(
  initialData: state$.value,
  stream: state$,
  builder: (context, snapshot) {
    final UiState state = snapshot.requireData;
    
    return ...;
  },
);

See also flutter_bloc_pattern/RxStreamBuilder, it can be used with StateStream perfectly and more easily (don't require initialData and don't need to call snapshot.requireData).

final StateStream<UiState> state$;

RxStreamBuilder<UiState>(
  stream: state$,
  builder: (context, UiState state) {
    // use state directly
    return ...;
  }
);

4. NotReplayValueStream

A Stream that provides synchronous access to the last emitted item, but not replay the latest value.

• Broadcast
  • ValueSubject
  • NotReplayValueConnectableStream
    • publishValueNotReplay
    • shareValueNotReplay
• Single-subscription
  • ValueStreamController
  • toNotReplayValueStream

5. Utils

DisposableMixin

A mixin that makes it easy to dispose streams without having to store and close a StreamSubscription variable.

Typical usage is as follows:

class DisposableExample with DisposableMixin {
  DisposableExample({
    required Stream<DateTime> dateTimeStream,
  }) {
    dateTimeStream.takeUntil(dispose$).listen(
          (value) => print('Disposable example: $value'),
        );
  }
}

License

MIT License

Copyright (c) 2020-2022 Petrus Nguyễn Thái Học