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watchFragment

Watch a GraphQL fragment in the cache and get updates when the fragment changes.

API​

Apollo.watchFragment<TData, TVariables>(
  options: WatchFragmentOptions<TData, TVariables>
): Observable<WatchFragmentResult<TData>>

Returns an Observable which emits the current fragment value in the cache. This observable is long-lasting and continues to deliver fragment value changes until unsubscribed from.

Watching a fragment​

this.apollo.watchFragment({
  fragment: AuthorFragmentDoc,
  from: {
    __typename: 'Author',
    id: '1'
  }
}).pipe(
  map(result => result.data as AuthorFragment)
);
tip

In the example above, __typename can be omitted (e.g. from: { id: '1' })
Apollo Orbit will automatically extract the type name from the first fragment definition it encounters in the document, even if it contains multiple fragments.