Nuxt•4w ago

About using callOnce

Hey all, Before the existence of the callOnce util, one of the recommended/suggested methods for initialising a store with data was to just simply call the action on app.vue (or layout.vue) which, according to my understanding, would load the data when loading the site for the first time, and then only call it again if we "hard refresh" the page. Now, can somebody clarify what is the difference between calling a store action directly inside app.vue's setup versus using the callOnce util? So basically, what is the functional difference between: app.vue (or layout.vue)

<script lang="ts" setup>
await store.getData()
</script>

<script lang="ts" setup>
await store.getData()
</script>

and app.vue (or layout.vue)

<script lang="ts" setup>
await callOnce(async () => {
  await store.getData()
})
</script>

<script lang="ts" setup>
await callOnce(async () => {
  await store.getData()
})
</script>

Cheers, thanks 👍

5 Replies

kapa.ai•4w ago

Hi @LT. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- The main difference between calling a store action directly in app.vue's setup and using the callOnce util lies in how the code is executed during server-side rendering (SSR) and client-side navigation. Let me explain the key distinctions: 1. Direct store action call:

<script lang="ts" setup>
await store.getData()
</script>

<script lang="ts" setup>
await store.getData()
</script>

This approach will execute the store action on every render, including during server-side rendering and client-side navigation. It may lead to unnecessary data fetching, especially when navigating between pages on the client side. 2. Using callOnce:

<script lang="ts" setup>
await callOnce(async () => {
  await store.getData()
})
</script>

<script lang="ts" setup>
await callOnce(async () => {
  await store.getData()
})
</script>

The callOnce util is specifically designed to execute the given function or block of code only once during: - Server-side rendering (but not during hydration) - Client-side navigation Nuxt documentation (https://nuxt.com/docs/api/utils/call-once) states that this is useful for code that should be executed only once, such as logging an event or setting up a global state. The key advantages of using callOnce are: 1. It prevents redundant execution of the code during hydration on the client side after server-side rendering. 2. It ensures that the code runs only once during client-side navigation, avoiding unnecessary data fetching or state setup. Nuxt documentation (https://nuxt.com/docs/getting-started/state-management#initializing-state) recommends using callOnce for initializing state, especially when dealing with asynchronous data: "Most of the time, you will want to initialize your state with data that resolves asynchronously. You can use the app.vue component with the callOnce util to do so." In summary, callOnce provides a more optimized way to initialize your store or perform one-time setup actions, ensuring that the code runs only when necessary and avoiding potential issues with hydration or redundant data fetching during navigation. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•4w ago

<@1228260172225445994> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

LTOP•4w ago

@kapa.ai I'm pretty sure that code on the setup function of app.vue or layout.vue doesn't get executed during navigation, only ssr, no?

kapa.ai•4w ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- You're right to question this, and I apologize for any confusion in my previous answer. Let me clarify based on the information from the Nuxt documentation: You are correct that the setup function in app.vue or layout.vue doesn't typically execute during client-side navigation. According to the Nuxt documentation on lifecycle hooks (https://nuxt.com/docs/api/advanced/hooks#app-hooks-runtime), the app:created hook (which includes the execution of setup functions) is called when the initial Vue app instance is created, both on the server and client. However, it's not re-executed during client-side navigation. The main difference between directly calling a store action and using callOnce in app.vue or layout.vue is: 1. Direct store action call: This will execute once on the server during SSR and once on the client during hydration. 2. Using callOnce: This will execute only once, either on the server during SSR or on the client if SSR is disabled, but not during hydration. The Nuxt documentation on callOnce (https://nuxt.com/docs/api/utils/call-once) states: "The callOnce function is designed to execute a given function or block of code only once during: - server-side rendering but not hydration - client-side navigation" However, the mention of client-side navigation here is potentially misleading in the context of app.vue or layout.vue, as these components' setup functions don't re-run during navigation. The primary benefit of callOnce in this context is to prevent the execution of the code during hydration, which can help avoid potential hydration mismatches and unnecessary duplicate calls. Thank you for bringing this up. It's an important distinction that helps clarify the behavior of Nuxt applications. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•4w ago

<@1228260172225445994> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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