Nuxt•3mo ago

[useAsyncData] handler must be a function.

I am trying to write an api utility function that wraps useAsyncData. I don't know if that idea is fraught with peril to begin with, but I am running up against an issue since this function is running in a utility within a setup store in pinia. The error I get running the following code:

const { data } = await nuxtApp.runWithContext(() => {
  const fetch = useRequestFetch();
  return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));
});
setApiSuccess(apiName, data.value);

const { data } = await nuxtApp.runWithContext(() => {
  const fetch = useRequestFetch();
  return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));
});
setApiSuccess(apiName, data.value);

Throws the [useAsyncData] handler must be a function. error. Is there something I can do around this?

2 Replies

kapa.ai•3mo ago

Hi @dmarr. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- The error [useAsyncData] handler must be a function. typically occurs when the second argument to useAsyncData is not a function. In your code, you are correctly passing a function as the handler:

return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));

return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));

However, there are a few important caveats when using useAsyncData: 1. Composables like useAsyncData must be called directly in the Nuxt context (e.g., in a setup function, plugin, or route middleware). They are not designed to be called inside arbitrary utility functions or within Pinia stores. This is because composables rely on the current Vue instance and Nuxt context, which may not be available or correct outside of these places. Calling them elsewhere can lead to errors or unexpected behavior [Nuxt useAsyncData docs]. 2. Pinia stores and composables: You should not call useAsyncData inside a Pinia store or from a utility function that is not directly in a setup context. If you need to fetch data in a store, use $fetch or another direct fetch method instead. useAsyncData is for SSR-friendly data fetching in components, not for store logic [Nuxt data fetching guide]. 3. Side effects and Pinia: Using useAsyncData to trigger Pinia actions or store mutations is discouraged and can cause repeated executions or unintended side effects [docs: add context for useAsyncData side effects]. What you should do: - If you want to fetch data in a Pinia store, use $fetch or a similar method, not useAsyncData. - If you want to wrap useAsyncData, do so in a composable that is called from a component's setup function, not from a store. Example:

// In a composable (not a store)
export function useApiData(apiName, url, searchParams, signal) {
  const fetch = useRequestFetch();
  return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));
}

// In a composable (not a store)
export function useApiData(apiName, url, searchParams, signal) {
  const fetch = useRequestFetch();
  return useAsyncData(apiName, () => fetch(url, { query: searchParams, signal }));
}

Then, in your component's <script setup>, you can use:

const { data } = await useApiData(apiName, url, searchParams, signal);

const { data } = await useApiData(apiName, url, searchParams, signal);

Summary:
You are seeing this error because useAsyncData is being called in a context where the Nuxt app instance is not available (such as inside a Pinia store or a non-setup utility). Move your data fetching logic to a composable or directly into your component's setup function to resolve this [Nuxt useAsyncData docs]. If you need to fetch data in a store, use $fetch instead [Nuxt data fetching guide]. If you need more advanced patterns, see the custom useFetch recipe for guidance on wrapping fetch logic in Nuxt. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•3mo ago

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[useAsyncData] handler must be a function.

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