jonnysamps

class WidgetService {
  constructor(private auth: AuthService, private apollo: Apollo){}

  // 1. BAD PRACTICE: keeps a separate member variable as the 
  //    subject that will get exposed to users
  //    of this class. This creates opportunity to simply
  //    call `next` whenever it is convenient instead of
  //    pipelining from the _source of truth_ observable to 
  //    create the intended behavior. This creates
  //    misdirection away from the source of truth

jonnysamps

export class WidgetService {

  constructor(
    private auth: AuthService,
    private apollo: Apollo,
  ) {}

  // 1. We still have a memoized member variable
  //    but this time it is an Observable (not a subject)
  //    and it gets created from piplining from our

jonnysamps

// Fires immediately and then on an interval
timer(0, REFRESH_INTERVAL)
  .pipe(
    mergeMap(() => apollo.query({ query: gql`...` })),
    map(result => result.data)
  )
  .subscribe(() => {
    // fires once per http request
  });

jonnysamps

const query = gql`...`;
timer(0, REFRESH_INTERVAL)
  .pipe(
    mergeMap(() => apollo.watchQuery({ query }).valueChanges),
    map(result => result.data)
  )
  .subscribe(() => {
    // ...
  });

jonnysamps

const query = gql`...`;
apollo.watchQuery({ 
  query,
  pollInterval: REFRESH_INTERVAL
}).valueChanges
  .pipe(
    map(result => result.data)
  )
  .subscribe(() => {
    // ...

jonnysamps

const query = gql`...`;
const watchQuery = apollo.watchQuery({ query }); 

watchQuery.valueChanges
  .pipe(
    map(result => result.data)
  )
  .subscribe(() => {
    // ...
  });