BehaviorSubject<T> class
A special StreamController that captures the latest item that has been added to the controller, and emits that as the first item to any new listener.
This subject allows sending data, error and done events to the listener. The latest item that has been added to the subject will be sent to any new listeners of the subject. After that, any new events will be appropriately sent to the listeners. It is possible to provide a seed value that will be emitted if no items have been added to the subject.
BehaviorSubject is, by default, a broadcast (aka hot) controller, in order
to fulfill the Rx Subject contract. This means the Subject's stream
can
be listened to multiple times.
Example
final subject = BehaviorSubject<int>();
subject.add(1);
subject.add(2);
subject.add(3);
subject.stream.listen(print); // prints 3
subject.stream.listen(print); // prints 3
subject.stream.listen(print); // prints 3
Example with seed value
final subject = BehaviorSubject<int>.seeded(1);
subject.stream.listen(print); // prints 1
subject.stream.listen(print); // prints 1
subject.stream.listen(print); // prints 1
- Inheritance
- Object
- Stream<
T> - StreamView<
T> - Subject<
T> - BehaviorSubject
- Implemented types
-
- ValueStream<
T>
- ValueStream<
- Available Extensions
- BufferExtensions
- ConcatExtensions
- ConnectableStreamExtensions
- DebounceExtensions
- DefaultIfEmptyExtension
- DelayExtension
- DistinctUniqueExtension
- DoExtensions
- EndWithExtension
- EndWithManyExtension
- ExhaustMapExtension
- FlatMapExtension
- GroupByExtension
- IgnoreElementsExtension
- IntervalExtension
- MapToExtension
- MaterializeExtension
- MaxExtension
- MergeExtension
- MinExtension
- OnErrorExtensions
- PairwiseExtension
- SampleExtensions
- ScanExtension
- SkipUntilExtension
- StartWithExtension
- StartWithManyExtension
- SwitchIfEmptyExtension
- SwitchMapExtension
- TakeUntilExtension
- TakeWhileInclusiveExtension
- ThrottleExtensions
- TimeIntervalExtension
- TimeStampExtension
- WhereTypeExtension
- WindowExtensions
- WithLatestFromExtensions
- ZipWithExtension
Constructors
- BehaviorSubject({void onListen(), void onCancel(), bool sync = false})
-
Constructs a BehaviorSubject, optionally pass handlers for
onListen
,onCancel
and a flag to handle eventssync
. [...]factory - BehaviorSubject.seeded(T seedValue, {void onListen(), void onCancel(), bool sync = false})
-
Constructs a BehaviorSubject, optionally pass handlers for
onListen
,onCancel
and a flag to handle eventssync
. [...]factory
Properties
- done → Future
-
A future which is completed when the stream controller is done
sending events. [...]
read-only, inherited
- errorAndStackTrace → ErrorAndStackTrace
-
Last emitted error and the corresponding stack trace,
or null if no error added or value exists.
See hasError
read-only, override
-
first
→ Future<
T> -
The first element of this stream. [...]
read-only, inherited
- hasError → bool
-
A flag that turns true as soon as at an error event has been emitted.
read-only, override
- hashCode → int
-
The hash code for this object. [...]
read-only, inherited
- hasListener → bool
-
Whether there is a subscriber on the
Stream
.read-only, inherited - hasValue → bool
-
A flag that turns true as soon as at least one event has been emitted.
read-only, override
- isBroadcast → bool
-
Whether this stream is a broadcast stream.
read-only, inherited
- isClosed → bool
-
Whether the stream controller is closed for adding more events. [...]
read-only, inherited
-
isEmpty
→ Future<
bool> -
Whether this stream contains any elements. [...]
read-only, inherited
- isPaused → bool
-
Whether the subscription would need to buffer events. [...]
read-only, inherited
-
last
→ Future<
T> -
The last element of this stream. [...]
read-only, inherited
-
length
→ Future<
int> -
The number of elements in this stream. [...]
read-only, inherited
- onCancel ↔ ControllerCancelCallback
-
The callback which is called when the stream is canceled. [...]
read / write, inherited
- onListen ↔ ControllerCallback
-
The callback which is called when the stream is listened to. [...]
read / write, inherited
- onPause ↔ ControllerCallback
-
The callback which is called when the stream is paused. [...]
read / write, inherited
- onResume ↔ ControllerCallback
-
The callback which is called when the stream is resumed. [...]
read / write, inherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited
-
single
→ Future<
T> -
The single element of this stream. [...]
read-only, inherited
-
sink
→ StreamSink<
T> -
Returns a view of this object that only exposes the
StreamSink
interface.read-only, inherited -
stream
→ ValueStream<
T> -
The stream that this controller is controlling.
read-only, override
- value ↔ T
-
Get the latest value emitted by the Subject
read / write, override-getter
Methods
-
add(
T event) → void -
Sends a data
event
. [...]inherited -
addError(
Object error, [StackTrace stackTrace]) → void -
Sends or enqueues an error event. [...]
inherited
-
addStream(
Stream< T> source, {bool cancelOnError = true}) → Future -
Receives events from
source
and puts them into this controller's stream. [...]inherited -
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)) → ValueStream<E> -
Transforms each element into a sequence of asynchronous events. [...]
override
-
asyncMap<
E> (FutureOr< E> convert(T event)) → ValueStream<E> -
Creates a new stream with each data event of this stream asynchronously
mapped to a new event. [...]
override
-
cast<
R> () → ValueStream< R> -
Adapt this stream to be a
Stream<R>
. [...]override -
close(
) → Future -
Closes the stream. [...]
inherited
-
contains(
Object needle) → Future< bool> -
Returns whether
needle
occurs in the elements provided by this stream. [...]inherited -
createForwardingSubject<
R> ({void onListen(), void onCancel(), bool sync = false}) → BehaviorSubject< R> -
Creates a trampoline StreamController, which can forward events
in the same manner as the original Subject does.
e.g. replay or behavior on subscribe.
override
-
distinct(
[bool equals(T previous, T next)]) → ValueStream< T> -
Skips data events if they are equal to the previous data event. [...]
override
-
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
index
th 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)) → ValueStream<S> -
Transforms each element of this stream into a sequence of elements. [...]
override
-
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 -
Executes
action
on each element of this stream. [...]inherited -
handleError(
Function onError, {bool test(Object error)}) → ValueStream< T> -
Creates a wrapper Stream that intercepts some errors from this stream. [...]
override
-
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. [...]
inherited
-
map<
S> (S convert(T event)) → ValueStream< S> -
Transforms each element of this stream into a new stream event. [...]
override
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed. [...]
inherited
-
onAdd(
T event) → void -
An extension point for sub-classes. Perform any side-effect / state
management you need to here, rather than overriding the
add
method directly.override -
onAddError(
Object error, [StackTrace stackTrace]) → void -
An extension point for sub-classes. Perform any side-effect / state
management you need to here, rather than overriding the
add
method directly.override -
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) → ValueStream< T> -
Skips the first
count
data events from this stream. [...]override -
skipWhile(
bool test(T element)) → ValueStream< T> -
Skip data events from this stream while they are matched by
test
. [...]override -
take(
int count) → ValueStream< T> -
Provides at most the first
count
data events of this stream. [...]override -
takeWhile(
bool test(T element)) → ValueStream< T> -
Forwards data events while
test
is successful. [...]override -
timeout(
Duration timeLimit, {void onTimeout(EventSink< T> sink)}) → ValueStream<T> -
Creates a new stream with the same events as this stream. [...]
override
-
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 -
Returns a string representation of this object.
inherited
-
transform<
S> (StreamTransformer< T, S> streamTransformer) → ValueStream<S> -
Applies
streamTransformer
to this stream. [...]override -
where(
bool test(T event)) → ValueStream< T> -
Creates a new stream from this stream that discards some elements. [...]
override
Operators
-
operator ==(
Object other) → bool -
The equality operator. [...]
inherited