segue to specific Firebase data - ios

Question

I have a tableView and it has about 5 cells and each cell has a different subject. Upon clicking on the cell, I will like to segue to a view controller that is populated with Firebase data only containing posts that has the specific subject clicked.
override func viewDidLoad() {
super.viewDidLoad()
FIRDatabase.database().reference().child("books").observeSingleEvent(of: .value, with: { (snapshot:FIRDataSnapshot) in
if let postsDictionary = snapshot .value as? [String: AnyObject] {
self.Category = postsDictionary["Category"] as? String ?? ""
}})
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "segue" {
let showBooks = segue.destination as! SearchTableViewController
showBooks.categorySegue = self.Category
}
}
In my Firebase database, I have a bunch of posts made by different users and in every post, they set the category to which the post belongs to. For example, if I click on the tableView cell that has the subject: Economics, I would like to segue to a view controller that only has the Economics category.
This is how I retrieve the post attributed to certain subjects:
databaseRef.child("books").queryOrdered(byChild: "category").queryEqual(toValue: categorySegue).observeSingleEvent(of: .value, with: { (snapshot) in
let key = snapshot.key
let snapshot = snapshot.value as? NSDictionary
snapshot?.setValue(key, forKey: "uid")
if(key == self.loggedUser?.uid)
{
print("same as logged in user")
}
else
{
self.usersArray.append(snapshot)
self.followUsersTableView.insertRows(at: [IndexPath(row:self.usersArray.count-1,section:0)], with: UITableViewRowAnimation.automatic)
}
}) { (error) in
print(error.localizedDescription)
}
tableView.tableFooterView = UIView()

Answer 1

If the category is directly below the posts node under a uniqueID, then try this
Example :
posts
-> post_id1
->category : "books"
-> other keys
-> post_id2
->category : "music"
-> other keys
The query to fetch the posts by category will be like this,
let strCategory = "music"
baseRef.child("posts").queryOrdered(byChild: "category").queryEqualToValue(strCategory).observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot)
})
To get the cell index on selection,
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let indexPath = tableView.indexPathForSelectedRow{
let selectedRow = indexPath.row
let categorySelected = Subjects[selectedRow]
}
}