flowr_dart 2.13.0

Base FlowR library for pure Dart

FlowR Dart

State management based on Reactive programming for pure Dart.

Install

dart pub add flowr_dart

Tip

If you are using Flutter, it is highly recommended to use the flowr package, which provides MVVM support and Flutter-specific features.

Getting started

import 'package:flowr_dart/flowr_dart.dart';

class Counter extends FlowR<int> {
  @override
  final int initValue;

  Counter({required this.initValue});

  incrementCounter() => update((old) {
        logger('incrementCounter: $old');
        return old + 1;
      });

  incrementSlowly() => update(
        (old) async {
          await Future<void>.delayed(const Duration(milliseconds: 300));
          return old + 1;
        },
        mutexTag: 'counter',
      );
}

Future<void> main() async {
  Logger.root.level = Level.INFO;
  Logger.root.onRecord.listen(LoggableMx.devLogRecordPrinter);

  final counter = Counter(initValue: 0);
  await counter.incrementCounter();
  print('counter: ${counter.value}');

  counter.dispose();
}

Core APIs

• FlowR<T> stores the current value in a ValueStream<T>.
• update reads the current value, runs an updater, catches failures, and calls put on success.
• runCatching is available for non-state work that should share the same error and skip handling.
• skpIf and skpNull throw SkipError, which stops the current flow without treating it as a failure.
• autoDispose(subscription) cancels registered stream subscriptions when dispose is called.

Concurrency

update and runCatching can be scheduled with:

• debounceTag: wait until calls stop, then run the last call.
• throttleTag: run at most once during the configured window.
• mutexTag: run immediately and ignore overlapping calls with the same tag.
• slowlyMs: window size in milliseconds for debounce and throttle.

Tags are scoped to the FlowR instance. Use stable tag values for each independent action.

ValueStream helpers

final names = counter.stream.distinctWith((count) => 'count: $count');
final evenValues = counter.stream.whereValue((count) => count.isEven);

• mapValue maps both stream events and synchronous value access.
• distinctBy keeps the latest emitted value for the selected key.
• distinctWith maps then de-duplicates mapped values.
• whereValue keeps the latest value that passed the filter. If no value has passed yet, hasValue is false, valueOrNull is null, and value throws.

Logging

FlowR uses package:logging. Configure the root logger once in your app:

Logger.root.level = Level.INFO;
Logger.root.onRecord.listen(LoggableMx.devLogRecordPrinter);

Set Logger.root.level = Level.FINE to see normal put, debounce, throttle, mutex, and SkipError logs.

Disposal

Call dispose when a FlowR instance is no longer used. This closes the state subject, cancels subscriptions registered through autoDispose, and disposes pending debounce, throttle, or mutex timers.

Run example

Demo FlowR: for dart main.dart

# From workspace root
dart run examples/example/lib/main.dart