til/groq/grab-values-from-an-array-of-references.md

Grab Values From An Array Of References

Let's say we have a post object in our schema. A post can have an array of references to tags telling you what topics the post covers. Each tag has a slug and we want to get the string value for each slug.

Let's say we are interested in the post with _id of 123.

Here is how we can achieve that with a groq query:

*[
  _type == 'post' && _id == 123
]{
  'tags': tags[]->slug.current
}.tags

=> ["javascript", "react-js"]

If the schema was such that each post just had a single tag reference, then you could write the chain of references as tag->slug.current. Because it is an array of references, we need the [] to declare that we want each value.

The -> operator follows the reference. Otherwise we'd just have access to the _ref and _type values.

The final .tags unnests the tags value we gathered into an object. Then the result is just the array of slug values.