ValueStream<T> class

A Stream that also exposes its current value synchronously.

Modeled on rxdart's ValueStream/BehaviorSubject: listening re-emits the current value first (captured at listen time), then every subsequent change. Unlike a plain stream, .value reads the latest value without subscribing — which removes the need for a parallel xNow getter alongside each stream.

The change stream is built lazily (on first subscription) and cached, so reading value alone never allocates it. This makes .value cheap whether or not the owner caches the ValueStream in a field.

Inheritance
Available extensions

Properties

changes → Stream<T>
The raw change stream: emits on every change, without re-emitting the current value on listen. Use this when you only want deltas; listen to the ValueStream itself (e.g. in a StreamBuilder) to get the current value first, then changes.
no setter
first → Future<T>
The first element of this stream.
no setterinherited
hashCode → int
The hash code for this object.
no setterinherited
isBroadcast → bool
Whether this stream is a broadcast stream.
no setteroverride
isEmpty → Future<bool>
Whether this stream contains any elements.
no setterinherited
last → Future<T>
The last element of this stream.
no setterinherited
length → Future<int>
The number of elements in this stream.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
single → Future<T>
The single element of this stream.
no setterinherited
value → T
The current value, read synchronously without subscribing.
no setter

Methods

accumulate({Duration? removeIfGone, bool coalesce = true}) → Stream<List<ScanResult>>

Available on Stream<ScanResult>, provided by the ScanResultAccumulate extension

Accumulates advertisements into a growing, de-duplicated device list, keyed by address.
any(bool test(T element)) → Future<bool>
Checks whether test accepts any element provided by this stream.
inherited
asBroadcastStream({void onListen(StreamSubscription<T> subscription)?, void onCancel(StreamSubscription<T> subscription)?}) → Stream<T>
Returns a multi-subscription stream that produces the same events as this.
inherited
asyncExpand<E>(Stream<E>? convert(T event)) → Stream<E>
Transforms each element into a sequence of asynchronous events.
inherited
asyncMap<E>(FutureOr<E> convert(T event)) → Stream<E>
Creates a new stream with each data event of this stream asynchronously mapped to a new event.
inherited
cast<R>() → Stream<R>
Adapt this stream to be a Stream<R>.
inherited
contains(Object? needle) → Future<bool>
Returns whether needle occurs in the elements provided by this stream.
inherited
distinct([bool equals(T previous, T next)?]) → Stream<T>
Skips data events if they are equal to the previous data event.
inherited
drain<E>([E? futureValue]) → Future<E>
Discards all data on this stream, but signals when it is done or an error occurred.
inherited
elementAt(int index) → Future<T>
Returns the value of the indexth data event of this stream.
inherited
every(bool test(T element)) → Future<bool>
Checks whether test accepts all elements provided by this stream.
inherited
expand<S>(Iterable<S> convert(T element)) → Stream<S>
Transforms each element of this stream into a sequence of elements.
inherited
firstWhere(bool test(T element), {T orElse()?}) → Future<T>
Finds the first element of this stream matching test.
inherited
fold<S>(S initialValue, S combine(S previous, T element)) → Future<S>
Combines a sequence of values by repeatedly applying combine.
inherited
forEach(void action(T element)) → Future<void>
Executes action on each element of this stream.
inherited
handleError(Function onError, {bool test(dynamic error)?}) → Stream<T>
Creates a wrapper Stream that intercepts some errors from this stream.
inherited
join([String separator = ""]) → Future<String>
Combines the string representation of elements into a single string.
inherited
lastWhere(bool test(T element), {T orElse()?}) → Future<T>
Finds the last element in this stream matching test.
inherited
listen(void onData(T value)?, {Function? onError, void onDone()?, bool? cancelOnError}) → StreamSubscription<T>
Adds a subscription to this stream.
override
map<S>(S convert(T event)) → ValueStream<S>
Like Stream.map, but preserves the value view: the result is a ValueStream whose current value is convert applied to this one's.
override
newStreamWithInitialValue(T initialValue) → Stream<T>

Available on Stream<T>, provided by the StreamNewStreamWithInitialValue extension

This stream with initialValue emitted first, to every listener. Broadcast-ness is preserved; the source is only subscribed while the returned stream has listeners.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
pipe(StreamConsumer<T> streamConsumer) → Future
Pipes the events of this stream into streamConsumer.
inherited
reduce(T combine(T previous, T element)) → Future<T>
Combines a sequence of values by repeatedly applying combine.
inherited
singleWhere(bool test(T element), {T orElse()?}) → Future<T>
Finds the single element in this stream matching test.
inherited
skip(int count) → Stream<T>
Skips the first count data events from this stream.
inherited
skipWhile(bool test(T element)) → Stream<T>
Skip data events from this stream while they are matched by test.
inherited
take(int count) → Stream<T>
Provides at most the first count data events of this stream.
inherited
takeWhile(bool test(T element)) → Stream<T>
Forwards data events while test is successful.
inherited
timeout(Duration timeLimit, {void onTimeout(EventSink<T> sink)?}) → Stream<T>
Creates a new stream with the same events as this stream.
inherited
toList() → Future<List<T>>
Collects all elements of this stream in a List.
inherited
toSet() → Future<Set<T>>
Collects the data of this stream in a Set.
inherited
toString() → String
A string representation of this object.
inherited
transform<S>(StreamTransformer<T, S> streamTransformer) → Stream<S>
Applies streamTransformer to this stream.
inherited
where(bool test(T element)) → Stream<T>
Creates a new stream from this stream that discards some elements.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited