StreamedValue

Intro

It's the simplest class that implements the StreamedObject interface. Every time a new value is set, this is compared to the oldest one and if it is different, it is sent to stream. Used in tandem with ValueBuilder it automatically triggers the rebuild of the widgets returned by its builder.

So for example, instead of:

counter += 1;
stream.sink.add(counter);

It becomes just:

counter.value += 1;

It can be used even with StreamedWidget and StreamBuilder by using its stream getter outStream. In this case, it is necessary to pass to the initialData parameter the current value of the StreamedValue (e.g. using the getter value).

N.B. when the type is not a basic type (e.g int, double, String etc.) and the value of a property of the object is changed, it is necessary to call the refresh method to update the stream.

Usage

// In the BLoC
final count = StreamedValue<int>(initialData: 0);

incrementCounter() {
  count.value += 2.0;
}

// View
ValueBuilder<int>(                
  stream: bloc.count, // no need of the outStream getter with ValueBuilder
  builder: (context, snapshot) =>
    Text('Value: ${snapshot.data}'),
  noDataChild: Text('NO DATA'),
),
RaisedButton(
    color: buttonColor,
    child: Text('+'),
    onPressed: () {
      bloc.incrementCounter();
    },
),

// As an alternative:
//
// StreamedWidget<int>(
//    initialData: bloc.count.value
//    stream: bloc.count.outStream,
//    builder: (context, snapshot) => Text('Value: ${snapshot.data}'),
//    noDataChild: Text('NO DATA'),
//),

On update the timesUpdated increases showing how many times the value has been updated.

N.B. For collections use StreamedList and StreamedMap instead.