fascinating-indigo

Is there a way to avoid union type with undefined for data that is returned by useQuery?

It seems that however I type the return type of queryFn or provide a generic type to useQuery, data will always be T | undefined. From the docs, I read that the value of data defaults to undefined, but I did not really understand what that means. Does it mean exactly what I am asking lol? That there will always be union with undefined?

16 Replies

fascinating-indigoOP•2y ago

after some more research I am guessing it's only normal that this is the case, before the fetching happens, or before checking cache, data will be undefined. Is that what is meant by data defaulting to undefined? curious why it's not null instead...

unwilling-turquoise•2y ago

null is a valid value to be returned from the queryFn undefined isn't

fascinating-indigoOP•2y ago

yes, I am talking about TypeScript though

fascinating-indigoOP•2y ago

For example

export async function getFreelancerReviews({
  queryKey
}: QueryFunctionContext): Promise<IFeedback[]> {
  const [_, userId] = queryKey;

  const { data } = await api.get('/api/v1/getuserreviews', { params: { user_id: userId } });

  return data;
}

export async function getFreelancerReviews({
  queryKey
}: QueryFunctionContext): Promise<IFeedback[]> {
  const [_, userId] = queryKey;

  const { data } = await api.get('/api/v1/getuserreviews', { params: { user_id: userId } });

  return data;
}

yet when I hover over data I get this

unwilling-turquoise•2y ago

you've already answered your own question

fascinating-indigoOP•2y ago

what does it mean in the docs that data Defaults to undefined?

unwilling-turquoise•2y ago

api.get can take 10 seconds. the component will still render in that time, with status: 'pending' and data: undefined I haen't written every sentence in the docs so i don't know

fascinating-indigoOP•2y ago

any reason why it's not null?

unwilling-turquoise•2y ago

we're going in circles now

null is a valid value to be returned from the queryFn undefined isn't

fascinating-indigoOP•2y ago

:( I am talking about data: undefined

unwilling-turquoise•2y ago

yes, you are asking why data isn't null when status is pending

fascinating-indigoOP•2y ago

correct

unwilling-turquoise•2y ago

and I'm answering with: becaus you could legally return null from your queryFn and then there wouldn't be any way to distinguish the two I could also say: because that's the way it was designed and we like undefined more than null. Is that better ?

fascinating-indigoOP•2y ago

ohhhhhhh now I perfectly understand you couldn't have phrased it better

unwilling-turquoise•2y ago

wow okay

fascinating-indigoOP•2y ago

apologies for my misunderstanding haha thank you so much!

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Is there a way to avoid union type with undefined for data that is returned by useQuery?

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