Subscriptions

The cache helpers subscription hooks are simple useEffect-based hooks that manage a Supabase Realtime subscription. Similar to the mutation hooks, the cache is automatically populated with the incoming data.

`useSubscription`

The useSubscription hook simply manages a realtime subscription. Upon retrieval of an update, it updates the cache with the retrieved data the same way the mutation hooks do. It exposes all params of the .on() method, including the callback, as well as the mutation options of the respective library.

import { useSubscription } from '@supabase-cache-helpers/postgrest-swr';
import { createClient } from '@supabase/supabase-js';
import { Database } from './types';
 
const client = createClient<Database>(
  process.env.SUPABASE_URL,
  process.env.SUPABASE_ANON_KEY
);
 
function Page() {
  const { status } = useSubscription(
    client,
    `random`,
    {
      event: '*',
      table: 'contact',
      schema: 'public',
    },
    ['id'],
    { callback: (payload) => console.log(payload) }
  );
 
  return <div>...</div>;
}

`useSubscriptionQuery`

The useSubscriptionQuery hook does exactly the same as the useSubscription hooks, but instead of updating the cache with the data sent by realtime, it re-fetches the entity from PostgREST and updates the cache with the returned data. The main use case for this hook are Computed Columns (opens in a new tab), because these are not sent by realtime. The callback passes an additional property data: R | T['Row'] which is populated with the data returned by the query. For DELETE events, data is populated with old_record for convenience.

import { useSubscriptionQuery } from '@supabase-cache-helpers/postgrest-swr';
import { createClient } from '@supabase/supabase-js';
import { Database } from './types';
 
const client = createClient<Database>(
  process.env.SUPABASE_URL,
  process.env.SUPABASE_ANON_KEY
);
 
function Page() {
  const { status } = useSubscriptionQuery(
    client,
    `random`,
    {
      event: '*',
      table: 'contact',
      schema: 'public',
    },
    ['id'],
    'id,username,has_low_ticket_number,ticket_number', // define the query to be executed when the realtime update arrives
    { callback: (payload) => console.log(payload) }
  );
 
  return <div>...</div>;
}

Mutations Custom Cache Updates