Apollo Client delete Item from cache

Question

Hy I'm using the Apollo Client with React. I query the posts with many different variables. So I have one post in different "caches". Now I want to delete a post. So I need to delete this specific post from all "caches".

const client = new ApolloClient({
    link: errorLink.concat(authLink.concat(httpLink)),
    cache: new InMemoryCache()
});

Postquery:

export const POSTS = gql`
    query posts(
        $after: String
        $orderBy: PostOrderByInput
        $tags: JSONObject
        $search: String
        $orderByTime: Int
    ) {
        posts(
            after: $after
            orderBy: $orderBy
            tags: $tags
            search: $search
            orderByTime: $orderByTime
        ) {
            id
            title
            ...
        }
    }
`;

I tried it with the cache.modify(), which is undefined in my mutation([https://www.apollographql.com/docs/react/caching/cache-interaction/#cachemodify][1])

const [deletePost] = useMutation(DELETE_POST, {
        onError: (er) => {
            console.log(er);
        },
        update(cache, data) {
            console.log(cache.modify())//UNDEFINED!!!
            cache.modify({
                id: cache.identify(thread), //identify is UNDEFINED + what is thread
                fields: {
                    posts(existingPosts = []) {
                        return existingPosts.filter(
                            postRef => idToRemove !== readField('id', postRef)
                         );
                    }
                }
            })
        }
    });

I also used the useApolloClient() with the same result.

THX for any help.

Ligetti

Answer 1

this option worked for me

const GET_TASKS = gql`
  query tasks($listID: String!) {
    tasks(listID: $listID) {
      _id
      title
      sort
    }
  }
`;

const REMOVE_TASK = gql`
  mutation removeTask($_id: String) {
    removeTask(_id: $_id) {
      _id
    }
  }
`;

const Tasks = () => {
  const { loading, error, data } = useQuery(GET_TASKS, {
    variables: { listID: '1' },
  });
  сonst [removeTask] = useMutation(REMOVE_TASK);

  const handleRemoveItem = _id => {
    removeTask({
      variables: { _id },
      update(cache) {
        cache.modify({
          fields: {
            tasks(existingTaskRefs, { readField }) {
              return existingTaskRefs.filter(
                taskRef => _id !== readField('_id', taskRef),
              );
            },
          },
        });
      },
    });
  };

  return (...);
};

Osculate

Answer 2

Instead of using cache.modify you can use cache.evict, which makes the code much shorter:

deletePost({
    variables: { id },
    update(cache) {
        const normalizedId = cache.identify({ id, __typename: 'Post' });
        cache.evict({ id: normalizedId });
        cache.gc();
    }
});

Phallicism

Is cache.gc() necessary in this case? – Andradite

I think it is, apollographql.com/docs/react/caching/garbage-collection/… says: "Evicting an object often makes other cached objects unreachable. Because of this, you should call cache.gc after evicting one or more objects from the cache." – Phallicism

This should be the accepted answer! – Polyphemus

i like it. simple and working – Chronometry

Answer 3

You can pass your updater to the useMutation or to the deletePost. It should be easier with deletePost since it probably knows what it tries to delete:

    deletePost({
        variables: { idToRemove },
        update(cache) {
            cache.modify({
                fields: {
                    posts(existingPosts = []) {
                        return existingPosts.filter(
                            postRef => idToRemove !== readField('id', postRef)
                        );
                    },
                },
            });
        },
    });

You should change variables to match your mutation. This should work since posts is at top level of your query. With deeper fields you'll need a way to get the id of the parent object. readQuery or a chain of readField from the top might help you with that.

Tarrel