Refetching Connections (Using and Changing Filters)

Often times when querying for a list of data, you can provide different values in the query which serve as filters that change the result set, or sort it differently.

Some examples of this are:

• Building a search typeahead, where the list of results is a list filtered by the search term entered by the user.
• Changing the ordering mode of the list comments currently displayed for a post, which could produce a completely different set of comments from the server.
• Changing the way News Feed is ranked and sorted.

Specifically, in GraphQL, connection fields can accept arguments to sort or filter the set of queried results:

fragment UserFragment on User {
  name
  friends(order_by: DATE_ADDED, search_term: "Alice", first: 10) {
    edges {
      node {
        name
        age
      }
    }
  }
}

In Relay, we can pass those arguments as usual using GraphQL variables

type Props = {
  userRef: FriendsListComponent_user$key,
};

function FriendsListComponent(props: Props) {
  const userRef = props.userRef;

  const {data, ...} = usePaginationFragment(
    graphql`
      fragment FriendsListComponent_user on User {
        name
        friends(
          order_by: $orderBy,
          search_term: $searchTerm,
          after: $cursor,
          first: $count,
        ) @connection(key: "FriendsListComponent_user_friends_connection") {
          edges {
            node {
              name
              age
            }
          }
        }
      }
    `,
    userRef,
  );

  return (...);
}

When paginating, the original values for those filters will be preserved:

type Props = {
  userRef: FriendsListComponent_user$key,
};

function FriendsListComponent(props: Props) {
  const userRef = props.userRef;

  const {data, loadNext} = usePaginationFragment(
    graphql`
      fragment FriendsListComponent_user on User {
        name
        friends(order_by: $orderBy, search_term: $searchTerm)
          @connection(key: "FriendsListComponent_user_friends_connection") {
          edges {
            node {
              name
              age
            }
          }
        }
      }
    `,
    userRef,
  );

  return (
    <>
      <h1>Friends of {data.name}:</h1>
      <List items={data.friends?.nodes}>{...}</List>

      {/*
       Loading the next items will use the original order_by and search_term
       values used for the initial query
      */ }
      <Button onClick={() => loadNext(10)}>Load more friends</Button>
    </>
  );
}

• Note that calling loadNext will use the original order_by and search_term values used for the initial query. During pagination, these value won't (and shouldn't) change.

If we want to refetch the connection with different variables, we can use the refetch function provided by usePaginationFragment, similarly to how we do so when Refetching Fragments with Different Data:

/**
 * FriendsListComponent.react.js
 */
import type {FriendsListComponent_user$key} from 'FriendsListComponent_user.graphql';

const React = require('React');
const {useState, useEffect} = require('React');

const {graphql, usePaginationFragment} = require('react-relay');


type Props = {
  searchTerm?: string,
  user: FriendsListComponent_user$key,
};

function FriendsListComponent(props: Props) {
  const searchTerm = props.searchTerm;
  const {data, loadNext, refetch} = usePaginationFragment(
    graphql`
      fragment FriendsListComponent_user on User {
        name
        friends(
          order_by: $orderBy,
          search_term: $searchTerm,
          after: $cursor,
          first: $count,
        ) @connection(key: "FriendsListComponent_user_friends_connection") {
          edges {
            node {
              name
              age
            }
          }
        }
      }
    `,
    props.user,
  );

  useEffect(() => {
    // When the searchTerm provided via props changes, refetch the connection
    // with the new searchTerm
    refetch({first: 10, search_term: searchTerm}, {fetchPolicy: 'store-or-network'});
  }, [searchTerm])

  return (
    <>
      <h1>Friends of {data.name}:</h1>

      {/* When the button is clicked, refetch the connection but sorted differently */}
      <Button
        onClick={() =>
          refetch({first: 10, orderBy: 'DATE_ADDED'});
        }>
        Sort by date added
      </Button>

      <List items={data.friends?.nodes}>...</List>
      <Button onClick={() => loadNext(10)}>Load more friends</Button>
    </>
  );
}

Let's distill what's going on here:

• Calling refetch and passing a new set of variables will fetch the fragment again with the newly provided variables. The variables you need to provide are a subset of the variables that the generated query expects; the generated query will require an id, if the type of the fragment has an id field, and any other variables that are transitively referenced in your fragment.
  • In our case, we need to pass the count we want to fetch as the first variable, and we can pass different values for our filters, like orderBy or searchTerm.
• This will re-render your component and may cause it to suspend (as explained in Loading States with Suspense) if it needs to send and wait for a network request. If refetch causes the component to suspend, you'll need to make sure that there's a Suspense boundary wrapping this component from above.
• Conceptually, when we call refetch, we're fetching the connection from scratch. It other words, we're fetching it again from the beginning and "resetting" our pagination state. For example, if we fetch the connection with a different search_term, our pagination information for the previous search_term no longer makes sense, since we're essentially paginating over a new list of items.

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