Can't load data when phone is offline in Expo app about electric

[linear]

VAX-1857 Why Electric can't load data when phone is offline?

[thunderfalco]

when device is offline, electric object always undefined, and return null.

[kevin-dp]

Hi @thunderfalco,

Below i pasted the relevant snippet from the example app:

const ElectricProviderComponent = ({
  children,
}: {
  children: React.ReactNode
}) => {
  const [electric, setElectric] = useState<Electric>()

  useEffect(() => {
    let isMounted = true

    const init = async () => {
      const config = {
        debug: DEBUG_MODE,
        url: ELECTRIC_URL,
      }

      const conn = SQLite.openDatabaseSync('electric.db')
      const client = await electrify(conn, schema, config)
      await client.connect(authToken())

      if (!isMounted) {
        return
      }

      setElectric(client)
    }

    init()

    return () => {
      isMounted = false
    }
  }, [])

  if (electric === undefined) {
    return null
  }

  return <ElectricProvider db={electric}>{children}</ElectricProvider>
}

The call to useEffect passes an empty array of dependencies, hence, the callback is executed when the component initially renders. Inside that useEffect callback we call the asynchronous init function which electrifies a local SQLite database:

const conn = SQLite.openDatabaseSync('electric.db')
const client = await electrify(conn, schema, config)
await client.connect(authToken())

The last line from the snippet above awaits the call to client.connect, i.e. it waits until we are connected with the Electric sync server. Since you're offline, this call blocks until you come online. Hence, while offline the code does not reach the setElectric(client) call and thus electric is always undefined. To solve this you could decide to only call client.connect once you detect that you're online or you could decide not to await the call. Ofcourse, when you're not connected to the sync server, writes won't propagate to and from other clients.

[kevin-dp]

I'm closing this issue as I believe my previous comment explains the behavior you're experiencing and this is not a bug. Feel free to re-open with a comment in case there is any problem.

[thunderfalco]

Thank you