Nuxt•10mo ago

useFetch, how to type correctly.

I have this useFetch:

const updateRef = ref(0)
const { data, status } = useFetch(`/api/v2/locations/${parsedId}`, {
    watch: [updateRef],
})

const updateRef = ref(0)
const { data, status } = useFetch(`/api/v2/locations/${parsedId}`, {
    watch: [updateRef],
})

The route always returns 'status'.
The optional return types are 'statusMessage', 'city', 'stones' and 'location'. The only type my IDE returns is 'status', as it's always present. How can I properly access optional fields without overriding the type in useFetch.

kapa.ai•3/10/25, 9:48 AM

Hi @Kyllian. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base.

kapa.ai•3/10/25, 9:48 AM

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To properly type your call to include optional fields, you need to provide a generic type parameter to . This allows TypeScript to know about all possible return fields, not just the ones that are always present.

Here's how you can properly type your call:

By providing the interface as a generic type parameter to , TypeScript will know that can have all these optional properties, even if they're not always returned from the API.

This approach is consistent with the Nuxt documentation on typing calls. The type signature for allows you to specify the data type as a generic parameter:

As shown in the Nuxt documentation for useFetch, this ensures that your IDE and TypeScript will recognize all the possible fields in the response.

Remember that is a ref, so you'll need to access the properties using in your code.
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kapa.ai•3/10/25, 9:48 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 9:50 AM

god this is absolute bollocks

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 9:51 AM

@kapa.ai Does Nuxt provide a way to simplify this?

{{ typeof stone.person === 'object' ? stone.person.name ?? "" : stone.person }}

kapa.ai•3/10/25, 9:51 AM

Let me check the knowledge base for you again. One moment!

kapa.ai•3/10/25, 9:52 AM

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Based on the knowledge sources provided, there isn't a specific Nuxt-provided utility function that directly simplifies this exact conditional expression pattern.

However, Nuxt does provide some related functionality that might be helpful in certain scenarios:

When working with data from API responses, you could use the system to ensure proper serialization/deserialization of complex objects:

For UI components, Nuxt UI (if you're using it) provides components like and that have built-in handling for displaying object properties through the prop:

Your specific conditional expression is a standard JavaScript pattern for safely accessing nested properties with fallbacks. While Nuxt doesn't have a built-in utility specifically for this pattern, you could create your own utility function if you use this pattern frequently:

Then use it in your template:

If you're looking for more advanced solutions for handling optional chaining and nullish coalescing in templates, you might want to consider using computed properties to simplify your template expressions.

kapa.ai•3/10/25, 9:52 AM

I hope this helps! Let me know if you need more specific guidance related to your Nuxt application.
----------------------
Note: you can ask me a follow up question by @ mentioning me again

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kapa.ai•3/10/25, 9:52 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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ᴋʏʟʟɪᴀɴOP•3/10/25, 9:54 AM

@kapa.ai how can I use a payload reducer in this:

const { data, status } = useFetch<{ city: any, location: ILocation, stones: IStone[] }>(, {
watch: [updateRef],
})

kapa.ai•3/10/25, 9:54 AM

Let me check the knowledge base for you again. One moment!

kapa.ai•3/10/25, 9:54 AM

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To use a payload reducer with , you need to use the option rather than a payload reducer directly. Payload reducers are specifically for the Nuxt payload system (used with ), while the option is what you need for transforming data from API responses with .

Here's how you can implement it:

The function allows you to modify the response data before it's stored in the Nuxt payload, which helps minimize payload size and ensures proper typing Docs > Getting-started > Data Fetching.

If you need to handle complex types like classes that aren't properly serialized by default, you can create a custom payload plugin to define reducers and revivers. This would be separate from your call:

kapa.ai•3/10/25, 9:54 AM

This plugin will handle the serialization/deserialization of your custom types throughout your Nuxt application, including data fetched with Docs > Api > Composables > useNuxtApp.

For more advanced serialization needs, you can also use an alternative serializer as shown in the Nuxt documentation Docs > Getting-started > Data Fetching.
----------------------
Note: you can ask me a follow up question by @ mentioning me again

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kapa.ai•3/10/25, 9:54 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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ᴋʏʟʟɪᴀɴOP•3/10/25, 9:56 AM

@kapa.ai

how would I parse types in useFetch using transform:

kapa.ai•3/10/25, 9:56 AM

Let me check the knowledge base for you again. One moment!

kapa.ai•3/10/25, 9:57 AM

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Your approach to using the function with is on the right track, but there are a few improvements we can make to ensure proper type handling.

Here's how you can correctly use the function to parse types in :

The key improvements in this approach:

It's generally better to create a new object rather than mutating the original response data
The function allows you to modify the data before it's stored in the Nuxt payload

This pattern is documented in the Nuxt documentation for data fetching, where the function is recommended for cases where you need more control over the response data or need to map over several objects Docs > Getting-started > Data Fetching.

If you're dealing with complex nested objects or arrays, you can perform more extensive transformations:

kapa.ai•3/10/25, 9:57 AM

Remember that the function doesn't prevent unwanted data from being fetched initially, but it will prevent unwanted data from being added to the payload transferred from server to client, which helps minimize payload size.
----------------------
Note: you can ask me a follow up question by @ mentioning me again

----------------------

kapa.ai•3/10/25, 9:57 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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ᴋʏʟʟɪᴀɴOP•3/10/25, 10:00 AM

@kapa.ai this messes with the typing

message.txt3.68KB

kapa.ai•3/10/25, 10:00 AM

Let me check the knowledge base for you again. One moment!

kapa.ai•3/10/25, 10:01 AM

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You're right to be concerned about how the function might affect typing in . The approach I suggested could indeed cause typing issues because TypeScript might not properly track the type transformations happening inside the function.

Here's a better approach that preserves proper typing:

The operator (available in TypeScript 4.9+) is particularly useful here as it ensures type conformity without altering the object's type, which is better than using type assertions with Github PR #28520.

Alternatively, if you're working with a version of TypeScript that doesn't support , you could define your transformations in a type-safe way:

kapa.ai•3/10/25, 10:01 AM

This approach ensures that TypeScript can properly track the types throughout the transformation process, maintaining type safety in your application.
----------------------
Note: you can ask me a follow up question by @ mentioning me again

----------------------

kapa.ai•3/10/25, 10:01 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 10:02 AM

cool so there is no way to have this structure

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 10:02 AM

so much for DRY

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 10:09 AM

@kapa.ai is there absolutely NO way to clean this

typeof data?.location.name === 'object' ? data?.location.name.en : data?.location.name || 'Loading'"

kapa.ai•3/10/25, 10:09 AM

Let me check the knowledge base for you again. One moment!

kapa.ai•3/10/25, 10:09 AM

----------------------
Based on the knowledge sources provided, there isn't a specific built-in Nuxt utility that directly simplifies this exact conditional expression pattern. However, I can suggest a few approaches to make your code cleaner while maintaining proper typing.

You could create a custom composable or utility function to handle this pattern:

Then in your component:

Alternatively, you could use a computed property to clean up your template:

The Nuxt documentation doesn't show a specific built-in utility for this exact pattern. The conditional expression you're using is a standard JavaScript pattern for safely accessing nested properties with fallbacks, and Nuxt doesn't have a specific shorthand for it.

If you're using this pattern frequently throughout your application, creating your own utility function as shown above would be the most maintainable approach.

I hope this helps! Let me know if you need more specific guidance related to your Nuxt application.
----------------------
Note: you can ask me a follow up question by @ mentioning me again

----------------------

kapa.ai•3/10/25, 10:09 AM

@166602211780984832 Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ᴋ

ᴋʏʟʟɪᴀɴOP•3/10/25, 10:10 AM

whoow lets replace a lot of code with even more code