How to get slug from a reference in Sanity?

Perfect! This is a common situation when working with references in Sanity. By default, references only return the _ref field (which is just the document ID), but you can easily get the full referenced document including the slug using the reference access operator (->).

Basic Solution

If you have a reference field like linkedPage, you can dereference it in your GROQ query using ->:

*[_type == "yourDocumentType"] {
  ...,
  linkedPage->
}

This will replace the reference with the entire referenced document, including the slug.

Getting Just the Slug

If you only need the slug (not the entire referenced document), you can project just that field:

*[_type == "yourDocumentType"] {
  ...,
  linkedPage->{
    slug
  }
}

Or even more concisely, access the slug directly:

*[_type == "yourDocumentType"] {
  ...,
  "pageSlug": linkedPage->slug.current
}

For Arrays of References

If you have an array of page references, you can dereference all of them:

*[_type == "yourDocumentType"] {
  ...,
  relatedPages[]->{
    slug
  }
}

The reference access operator works by internally executing a subquery to fetch the referenced document and merge it into your results. Just keep in mind that each -> does perform an additional query, so be mindful of performance when dereferencing large arrays or deeply nested references.