Hey! Do you have a nice way of updating the attributes of a growthbook instance through the lifetime of a Nextjs app? I currently do it like this

export const useSetGrowthbookAttributes = (
  attributes: Record<string, string | number | boolean>
) => {
  const gb = useGrowthBook();
  useEffect(() => {
    gb?.setAttributes(attributes);
  }, []);
};

But would love to hear other ideas!

Hi! I think that's generally the right approach when a specific page or component needs to have control over it's attributes . One thing to note is that

setAttributes

completely overwrites all existing attributes. If you want to be able to set partial attributes, you can do:

gb.setAttributes({
  ...gb.getAttributes(),
  ...attributes
})

In a lot of cases, attributes can be set at a higher level, like in

_app.tsx

or in your auth handler. For example, this in _app.tsx will keep a URL attribute up to date as you navigate the app:

const router = useRouter()

useEffect(() => {
  const update = (url) => {
    gb.setAttributes({
      ...gb.getAttributes(),
      url: url
    })
  }
  router.events.on('routeChangeStart', update)
  return () => router.events.off('routeChangeStart', update)
}, [])

Nice, thanks! Do you currently support/have a best practice for stickiness in feature/experiment variations when going from an anonymous user to a logged in state? e.g. I can say that I want users to be split by

id

in growthbook, but if I have a page that is shown to both anonymous and logged in users, I want them to have the same experience when logging in. If I generate a random ID when they first land on the page, how do I make sure that they see the same variant when they log in (I would like to tie the userId to

id

when logged in)?

We recommend keeping the attributes consistent. So

id

would always be the logged-in user id (or null or empty string when anonymous). And a second

sessionId

or similar would always be set for everyone and based on a cookie or local storage value.

Yeah that makes sense. So just keep

id

in the attributes after they log in while using the

sessionId

for assigning variants. Thanks!