how to use post method and pass params in swr? about swr

[sergiodxa]

SWR is more intended to get data, not update it, usually you have another function to update and after it you will run mutate to update the cache and trigger a revalidation (SWR will fetch it again)

[shuding]

UPDATE 2022.6:

SWR 2.0 beta now has a dedicated API for one-off requests such as POST. Docs and examples can be found here:

https://github.com/vercel/swr/releases/tag/2.0.0-beta.0

It also supports many good things such as cache population, error rollback and race condition prevention.

---

Original answer:

function App() {
  const { data } = useSWR('/api/data', fetch) // <--------------GET

  return <>
    {data}
    <button onClick={() => {
      fetch('/api/data', { method: 'POST', body: ... })  // <---POST
    }}>update data</button>
  </>
}

You can just use fetch for POST requests. I don't see the benefit of allowing POST in SWR.
And most importantly, most of the great features will be gone with POST (because it's not a "pure" action like GET, which is perfect for fetch-as-you-render):

• stale-while-revalidate (SWR)
• focus revalidate / polling
• automatically request deduplication
• caching
• ...

But speaking of revalidation/mutation, it's still a thing for allowing POST together with SWR. Currently we need to do this:

mutate('/api/data', newData, false) // local mutate without revalidation
await sendPost('/api/data', newData) // POST request
trigger('/api/data') // revalidate

Maybe we can simplify it to something like:

mutate('/api/data', newData, sendPost)

which will do the exact same thing as above.

[nicolasschabram]

Maybe it'd be worth checking out react-query's useMutation() hook for reference as well.

[eric-burel]

Answers here are assuming that POST = data mutation
However POST is legitimately needed when doing list filtering that will explode the URL limitation of GET requests.

Multiple arguments help a lot here, the second argument can be "fetch" call options: https://swr.vercel.app/docs/arguments#multiple-arguments

[DeepakKapiswe]

I Used like this and it worked for me, please let me know If I’m missing something

let url = 'some url here';

export default function ComponentName  (props) {
  const fetcher = (...args) => fetch(url, {
    method: 'post',
    headers: {
      "Content-Type": "application/json"
    },
    body: JSON.stringify(props.payload)
  }).then(res => res.json())

  const { data, error} = useSWR(url, fetcher, { suspense: true });

[monman2l]

const fetcher = params => url => post(url, params)
const { data, error } = useSWR('/api/user', fetcher({key: val}))

This way?

[pedronauck]

So, this should be work in the newest version (dependent data and multiple params):

const { data: user } = useSWR('/api/user')
const params = useMemo(() => {
  return { username: user && user.username }
}, [user])

const profile = useSWR(() => ['/api/profile', params])

Because I'm trying this and I'm getting an infinite loop always 😕

[shuding]

@iammarkps thanks for elaborating! 👍

Now I can understand your use case, it makes perfect sense.

Can SWR pass 2 arguments to functions?

And yes! This feature will solve the problem: #98

We just shipped it to [email protected] and you can use it but the documentation is not yet updated. Ideally your code will be:

useSWR([type, param], fetchFromFirebase)

But keep in mind it compares arguments shallowly, so keep in mind to memorize the object:

const param = useMemo(() => ({ submission_id: id }), [id])
useSWR(['getDetailedSubmissionData', param], fetchFromFirebase)

[iammarkps]

@quietshu Thank you! I've just improved it with your suggestion in this commit

[sergiodxa]

This example https://github.com/zeit/swr/tree/master/examples/optimistic-ui does something similar, update and then revalidate

[iammarkps]

I have a use case with firebase onCall function(which it's method is POST). Because it supports authentication by default, I have to use this workaround.

import firebase from '../lib/firebase'

export const fetchSubmissionData = async (id: string) => {
  const getSubmission = firebase
    .app()
    .functions('asia-east2')
    .httpsCallable('getDetailedSubmissionData')

  return await getSubmission({ submission_id: id })
}

Then I can use

 const { data } = useSWR(`${id}`, fetchSubmissionData)

My function is onCall because it needs to verify user before sending back data.

Any idea on improving this? @quietshu

[shuding]

@iammarkps can you show me a POST example you have without using SWR?

[iammarkps]

I always use it that way. But I'm just curious that, can I have only 1 global function to use firebase callable function?

Now I have to implement 3 different functions with same logic.

https://github.com/programming-in-th/programming.in.th/blob/master/src/utils/fetcher.ts

Because firebase callable function receives 2 args, not 1 like normal GET request(Just url of API).
Can SWR pass 2 arguments to functions?

PS.Pardon my bad english

[iammarkps]

I've used to do this when I was using redux (It's POST method).

https://github.com/programming-in-th/programming.in.th/blob/83ff9a23648e9ece55f8abeb555292da28908dac/src/redux/actions/submission.ts#L24

and this for normal data fetching (Still POST method)

https://github.com/programming-in-th/programming.in.th/blob/83ff9a23648e9ece55f8abeb555292da28908dac/src/redux/actions/task.ts#L34

But now I've converted it to normal http GET not firebase callable anymore.

https://github.com/programming-in-th/cloud_functions/blob/master/functions/src/tasks.ts#L4

So it works perfectly with SWR.

But I can't convert this to http GET, because I have to check user right to access the code in line 187. So I need to depend on firebase request context. @quietshu

[iammarkps]

I want to do this

export const fetchFromFirebase = async (type: string, param?: Object) => {
    const get = firebase
    .app()
    .functions('asia-east2')
    .httpsCallable(type)

  return await get(param)
}

[shuding]

@iammarkps looks great!

[shuding]

@pedronauck oh that's because you're using a function which returns an array here:

const profile = useSWR(() => ['/api/profile', params])

This case is not yet covered (thanks for reporting!), for now you can just use an array:

const profile = useSWR(['/api/profile', params])

[theweiweiway]

Hi! Great library, I had a quick question:

const profile = useSWR(() => ['/api/profile', params])

Right now, it's fetching whenever any attribute of params changes. Is there a way for me to programatically make it fetch with updated params only when a specific attribute of params changes?

Thanks

[sergiodxa]

You need to pass every attribute inside params as different elements of the array.

[yufengwang]

mark