FutureSubject<T> class

A FutureSubject takes a Function returning a Future of argument type T. The FutureSubject will call the argument future and use the result to build a DataNode using the argument builder Function. The built DataNode is then used as the notifier of the FutureSubject.

Example:

// A reference to an int
class IntReference {
  int value;
  IntReference(this.value);
}

/// Increments a [IntReference] by the `step` value.
class IncrementIntReference extends DataNode<IntReference> {
  final int step;
  IncrementIntReference(this.step, IntReference data) : super(data);

  @override
  Status update() {
    print('increment by $step');
    data.value += step;
    return Status.success;
  }
}

void futureSubjectExample() {
  // keep a scopy reference for testing purposes
  final intReference = IntReference(0);

  final futureSubject = FutureSubject<IntReference>(
    future: () async {
      // simulate some future based operation
      print('calling future');
      await Future<void>.delayed(const Duration(seconds: 2));
      // return a value from the future
      return intReference;
    },
    // builds a DataNode using the result of the future
    builder: (data) {
      return IncrementIntReference(5, data);
    },
  );

  final observer = Observer(handler: (subject) {
    print('notified by future subject: ${intReference.value}');
  });

  futureSubject.subscribe(observer);

  // calls the future function and notifies the
  // observer using the built DataNode when the
  // future completes
  futureSubject.update();
}

Inheritance

• Object
• Node
• Subject
• FutureSubject

Constructors

FutureSubject({required Future<T> future(), required DataNode<T> builder(T), List<Status> notifications = const [Status.success]})

Constructs a FutureSubject instance.

Properties

hashCode → int

The hash code for this object.

no setter, inherited

notifications → Status

final, inherited

notifier ↔ Node

getter/setter pair, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

notify() → void

Notifies each _ObserverBase by calling their respective receive(subject) method and passing this as the _SubjectBase of the notification.

inherited

rebuild() → void

Schedules the future to be called and the notifier DataNode to be rebuilt using the result of the future.

reset() → void

Resets the notification Node.

inherited

subscribe(_ObserverBase observer) → void

Add an _ObserverBase to the notification list.

inherited

toString() → String

A string representation of this object.

inherited

unsubscribe(_ObserverBase observer) → void

Remove an _ObserverBase from the notification list.

inherited

update() → Status

Calls the future and once a result is available the contained data is updated and the FutureSubject is updated as if it were a DataSubject.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited