Apollo Client delete Item from cache - reactjs

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.

Answer 1

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();
}
});

Answer 2

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 (...);
};

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.