Filter array of strings in Sanity query returning null

I can help you with filtering an array of strings in GROQ! Based on your example where platform is an array like ['ios', 'android'], here are the correct ways to filter it:

If you want to filter documents where platform contains a specific value:

*[_type == 'bannerQueue' && "ios" in platform] {
  banners[]->{
    _id,
    bannerType,
    "description": description[$lang],
    "imageUrl": image.asset->url,
    platform,
  }
}[0]

The in operator checks if a value exists in an array. So "ios" in platform returns true if the platform array contains "ios".

If you want to filter banners based on their platform array:

*[_type == 'bannerQueue'] {
  banners[]->{
    _id,
    bannerType,
    "description": description[$lang],
    "imageUrl": image.asset->url,
    platform,
  }["ios" in platform || "android" in platform]
}[0]

Here you're dereferencing the banners first with []->, then filtering the results with another filter that checks if the platform array contains your desired values.

Common reasons for getting null:

1. Missing the in operator - You need "ios" in platform, not platform == "ios"
2. Filter placement - Make sure your filter comes after the dereference operator (->) if you're filtering the referenced documents
3. Array syntax - Remember to use []-> when dereferencing an array of references

The key insight from the GROQ documentation is that the in operator is specifically designed for matching values in arrays: *["sci-fi" in genres] matches all documents where genres is an array containing the value "sci-fi".

Try the first example if you're filtering at the bannerQueue level, or the second if you need to filter the individual banners after dereferencing them!