How to filter Sanity array to return single object by ID, not empty objects

I understand your issue! You want to filter a nested array within a document to get only the single matching vanguard object by its ID, rather than getting an array with empty objects.

The key is to use GROQ's array filtering with projection to select just the matching object from your Vanguards array. Here are a few approaches:

Option 1: Filter the array and get the first match

*[_type == "VanguardsList"][0] {
  "vanguard": Vanguards[id == $slug][0]
}

This returns just the matching vanguard object directly.

Option 2: Inline the result (most common for Next.js)

*[_type == "VanguardsList"][0].Vanguards[id == $slug][0]

This gives you the single vanguard object directly, which is perfect for getStaticProps().

Option 3: More explicit projection

*[_type == "VanguardsList"][0] {
  "vanguard": Vanguards[id == $slug][0] {
    id,
    // ... other fields you want
  }
}

In your Next.js getStaticProps():

export async function getStaticProps({ params }) {
  const slug = params.slug; // or however you're getting the id
  
  const query = `*[_type == "VanguardsList"][0].Vanguards[id == $slug][0]`;
  
  const vanguard = await client.fetch(query, { slug });
  
  return {
    props: {
      vanguard
    }
  };
}

The key differences from what you were likely doing:

• Use [id == $slug] to filter the array to only matching items (where $slug is a parameter you pass to the query)
• Use [0] at the end to get the first (and only) match as an object, not an array
• The .Vanguards syntax directly accesses the array property

This approach avoids getting an array with empty objects because you're filtering the nested array before the final selection, and [0] returns a single object rather than an array.

If you're still seeing empty objects, make sure:

1. The id field in your vanguard objects matches exactly (case-sensitive)
2. You're passing the parameter correctly to your query
3. The field name is Vanguards (capital V) as shown in your structure