How to ignore error when use refreshInterval?

[Sara2009]

I just what to handle the error when first to fetch data. If the fetching data is triggered by the refreshInterval. I don't want to do anything. How can I config the useSWR?

[ErnestBrandi]

Well you don't have to do anything then... Just don't handle the error as you said.

[Sara2009]

But it will also trigger onError function. I cannot figure out them.

const { data, error } = useSWR(
    'api/fetchPKRankData',
    () => {
      return fetchData();
    },
    {
      refreshInterval: 15000,
      onError(err) {
          window.alert(err);
      }
    },
  );

[shuding]

It sounds weird to me to "ignore error", IMO every error should notify you. If you want to only show the error alert or notification for the first time, you should consider doing this (which is not in the scope of SWR):

// global level
const errorOccurred = {}

// component
const { data, error } = useSWR(
    key,
    fetcher,
    {
      refreshInterval: 15000,
      onError(err) {
        if (errorOccurred[key]) return
        errorOccurred[key] = true
        window.alert(err)
      }
    },
  )

Hope that helps!

[Sara2009]

Thanks a lot. It works. I just want to show the error alert for the first time when open the page. The list data in the page needs to be updated quietly using refreshInterval. So i want to ignore the polling refresh error. But i find the refresh will stop if the fetcher returns a reject. But i need the refresh continues.

[shuding]

Then you can do this, instead of throwing you can wrap it with another layer to say it's data or error:

const { data } = useSWR(
    key,
    async (url) => {
      try {
        return {
          data: await fetcher(url)
        }
      } catch (err) {
        return {
          error: err
        }
      }
    { refreshInterval: 15000 },
  )

const realData = data.data
const realError = data.error

Since fetcher will no longer throw, it will just keep polling. And you can handle data/error with realData and realError.

[Sara2009]

Thanks a lot. I'll try it.