Efficiently determine if user liked post in Firebase - ios

Question

I have an app where users can like posts and I want to determine if the current user has previously liked a post in an efficient manner. My data currently looks like this:
I also store the likes for every user
In my current query I am doing this:
if let people = post["peopleWhoLike"] as? [String: AnyObject] {
if people[(Auth.auth().currentUser?.uid)!] != nil {
posst.userLiked = true
}
}
However, I believe this requires me to download all of the post's likes which isn't very efficient, so I tried this:
if (post["peopleWhoLike\(Auth.auth().currentUser!.uid)"] as? [String: AnyObject]) != nil {
posst.userLiked = true
}
The second method doesn't seem to be working correctly. Is there a better way to do this?
Here is my initial query as well:
pagingReference.child("posts").queryLimited(toLast: 5).observeSingleEvent(of: .value, with: { snap in
for child in snap.children {
let child = child as? DataSnapshot
if let post = child?.value as? [String: AnyObject] {
let posst = Post()
if let author = post["author"] as? String, let pathToImage = post["pathToImage"] as? String, let postID = post["postID"] as? String, let postDescription = post["postDescription"] as? String, let timestamp = post["timestamp"] as? Double, let category = post["category"] as? String, let table = post["group"] as? String, let userID = post["userID"] as? String, let numberOfComments = post["numberOfComments"] as? Int, let region = post["region"] as? String, let numLikes = post["likes"] as? Int {

Answer 1

Solved it:
In the tableView I just query for the liked value directly and then determine what button to display.
static func userLiked(postID: String, cell: BetterPostCell, indexPath: IndexPath) {
// need to cache these results so we don't query more than once
if newsfeedPosts[indexPath.row].userLiked == false {
if let uid = Auth.auth().currentUser?.uid {
likeRef.child("userActivity").child(uid).child("likes").child(postID).queryOrderedByKey().observeSingleEvent(of: .value, with: { snap in
if snap.exists() {
newsfeedPosts[indexPath.row].userLiked = true
cell.helpfulButton.isHidden = true
cell.notHelpfulButton.isHidden = false
}
})
likeRef.removeAllObservers()
}
}
}
Called in my TableView:
DatabaseFunctions.userLiked(postID: newsfeedPosts[indexPath.row].postID, cell: cell, indexPath: indexPath)