How to conditionally load data with SWR

Using SWR you might have this problem: you want to do the request only if you have some data.

For example, one case I had was, I had to figure out if the user was logged in before sending a request to a /api/user endpoint to get the user’s data.

In particular, I had a session object, and inside it, a user object. Both needed to be defined.

So here’s what I did:

import fetcher from 'lib/fetcher'

...

const { data: userData } = useSWR(session && session.user ? `/api/user` : null, fetcher)

The first parameter is the URL. If it’s null, then SWR does not perform the request, and solves the original problem.