Document how to batch RTK Query mutations properly

I feel that the documentation needs to cover the following scenario.

I have an array of objects that I need to send to the API. The API only allows mutating one object per request. What is a good way to do this while:

• avoiding a race condition where the final cache invalidation is ignored because the second to last cache provide comes later.
• even better, firing just one cache invalidation after all mutations have been sent.

I understand mutations can probably use a queryFn to do this, but the docs only cover how to do multiple fetches.

[torhovland]

Thanks, that helped. I was able to get it working using this:

    updateAccessLevelRequests: builder.mutation<number, AccessLevelRequest[]>({
      async queryFn(accessLevelRequests, _queryApi, _extraOptions, baseQuery) {
        for (const accessLevelRequest of accessLevelRequests) {
          await baseQuery({
            url: `access-level-requests/${accessLevelRequest.id}/`,
            method: 'PUT',
            body: accessLevelRequest,
          });
        }
        return { data: accessLevelRequests.length };
      },
      invalidatesTags: ['AccessRequests'],
    }),

I still think it would be good to show this in the docs, though.

[giladv]

@phryneas just wanted to add that this is not a good solution when using an auto generated RTK api file. manually adding queries in this use case is beating the purpose. RTK Query needs a proper way to batch multiple mutations and merge their respective invalidation tags when they’re both done. otherwise there are use cases where race conditions occur.