#CollectionKey based component type safety

8 messages · Page 1 of 1 (latest)

dense daggerBOT
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Hi @prime salmon. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

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In your code, you are trying to use CollectionKey to achieve type safety. CollectionKey is a string union of all collection names defined in your src/content/config.* file. This type can be useful when defining a generic function that accepts any collection name. However, it seems like you are trying to use it as a type for the listType prop and then use it to type the CollectionEntry.

The CollectionEntry utility is used to correctly type your components props using TypeScript. This utility takes a string argument that matches the name of your collection schema, and will inherit all of the properties of that collection’s schema.

However, TypeScript does not support using a variable (in this case listType) as a type argument. TypeScript requires that type arguments be known at compile time, but the value of listType is only known at runtime.

Therefore, you cannot use CollectionEntry<typeof listType>[] as you are trying to do in your code. Instead, you would need to create a specific type for each of your collections and use conditional types or a mapping object to select the correct type based on the listType prop.

Here is an example of how you might do this:

type BlogCollectionEntry = CollectionEntry<'blog'>;
type NewsletterCollectionEntry = CollectionEntry<'newsletter'>;
// Add more types as needed...

type CollectionEntries = {
  blog: BlogCollectionEntry;
  newsletter: NewsletterCollectionEntry;
  // Add more entries as needed...
};

type Props = {
  listType: keyof CollectionEntries;
};

const { listType } = Astro.props;

const data = (await getCollection(listType)).sort((a, b) => b.data.creationDate.valueOf() - a.data.creationDate.valueOf()) as CollectionEntries[typeof listType][];
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In this example, CollectionEntries is a mapping object that maps collection names to their corresponding types. Then, CollectionEntries[typeof listType][] is used to select the correct type based on the listType prop.

Please note that this is a simplified example and you might need to adjust it based on your specific needs and the structure of your collections.

For more information, you can refer to the Astro documentation (https://docs.astro.build/en/guides/content-collections#passing-content-as-props) and the Astro API reference (https://docs.astro.build/en/reference/api-reference#other-content-collection-types).

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

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prime salmon
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@dense dagger i get the same error i was getting before
Property 'data' does not exist on type 'unknown'

dense daggerBOT
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Let me check the knowledge base for you. One moment! :books:

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The error message Property 'data' does not exist on type 'unknown' typically occurs when TypeScript cannot infer the type of a variable, and it defaults to the unknown type. In this case, it seems like TypeScript is unable to infer the type of the data property in your code.

In your code, you are trying to access the data property of each collection entry in the sort function. However, because of the type issue with CollectionEntry<typeof listType>[], TypeScript cannot guarantee that the data property exists on each collection entry.

To fix this issue, you need to ensure that TypeScript can infer the correct type for your collection entries. As I mentioned in the previous response, you cannot use CollectionEntry<typeof listType>[] because TypeScript does not support using a variable as a type argument.

Instead, you can use a type assertion to tell TypeScript that you are sure about the type of the collection entries. Here is an example of how you might do this:

type BlogCollectionEntry = CollectionEntry<'blog'>;
type NewsletterCollectionEntry = CollectionEntry<'newsletter'>;
// Add more types as needed...

type CollectionEntries = {{
  blog: BlogCollectionEntry[];
  newsletter: NewsletterCollectionEntry[];
  // Add more entries as needed...
}};

type Props = {{
  listType: keyof CollectionEntries;
}};

const {{ listType }} = Astro.props;

const data = (await getCollection(listType)) as CollectionEntries[typeof listType];

data.sort((a, b) => b.data.creationDate.valueOf() - a.data.creationDate.valueOf());

In this example, CollectionEntries is a mapping object that maps collection names to arrays of their corresponding types. Then, CollectionEntries[typeof listType] is used to assert the type of the collection entries.