INotification

Types

interface INotification<GName extends string, GValue> {
  readonly name: GName;
  readonly value: GValue;
}

Definition

A Notification is used as a replacement of the next, complete and error events: you will emit directly a INextNotification instead of calling subscriber.next() for example.

To create a Notification, you may use a plain object { name, value } or use the function createNotification.

Moreover, you may use some pre-existing Notifications:

• INextNotification
• ICompleteNotification
• IErrorNotification

Examples

Create an Observable from a Promise

type IObservableFromPromiseNotifications<GValue> =
  | INextNotification<GValue>
  | ICompleteNotification
  | IErrorNotification
  ;

function fromPromise<GValue>(
  promise: Promise<GValue>,
): IObservable<IObservableFromPromiseNotifications<GValue>> {
  type GNotificationsUnion = IObservableFromPromiseNotifications<GValue>;
  return (emit: IObserver<GNotificationsUnion>): IUnsubscribe => {
    let running: boolean = true;
    promise
      .then(
        (value: GValue) => {
          if (running) {
            emit(createNextNotification<GValue>(value));
          }
          if (running) {
            emit(createCompleteNotification());
          }
        },
        (error: any) => {
          if (running) {
            emit(createErrorNotification<any>(error));
          }
        }
      );
    return (): void => {
      running = false;
    };
  };
}

Consume the notifications

const subscribe = fromPromise(Promise.resolve(5));

subscribe((notification: IObservableFromPromiseNotifications<number>) => {
  switch (notification.name) {
    case 'next':
      console.log('next', notification.value);
      break;
    case 'complete':
      console.log('resolved');
      break;
    case 'error':
      console.log('rejected', notification.value);
      break;
  }
});

Output:

next: 5
resolved

You may also use the function notificationObserver if you prefer:

subscribe(
  notificationObserver({
    next: (value: number) => {
      console.log('next', value);
    },
    complete: () => {
      console.log('resolved');
    },
    error: (error: any) => {
      console.log('rejected', error);
    },
  }),
);