retrieving data from auto id database child - swift

Question

I'm kinda new on swift programming, my case is:
I have a database on firebase realtime "see picture", I want to retrieve the firstName and lastName data of a specific ID only.
for example:
When i'm at login screen and logged in using this email: "ali_y_k#hotmail.com", and when going to the next screen i want to display the firstName and lastName of this email in the text fields showing on picture
I have tried several solutions but the problem always was I can't enter the random IDs child to fetch the firstName and lastName
there is what i tried:
First
func retriveInfo () {
let databaseRef = Database.database().reference().child("User_Informations")
databaseRef.observe(.childAdded) { (snapshot) in
let snapshotValue = snapshot.value as! Dictionary<String,String>
let firstName = snapshotValue["firstName"]!
let lastName = snapshotValue["lastName"]!
let email = snapshotValue["email"]!
print(firstName,lastName,email)
}
}
This is printing all data (firstName,lastName,email) from every id
Second
func retriveInfo() {
let databaseRef = Database.database().reference().child("User_Informations")
databaseRef.observeSingleEvent(of: .value, with: { (snapshot) in
for snap in snapshot.children {
let userSnap = snap as! DataSnapshot
let uid = userSnap.key //the uid of each user
let userDict = userSnap.value as! [String:AnyObject] //child data
let firstName = userDict["firstName"] as! String
let lastName = userDict["lastName"] as! String
print("key = \(uid) First Name = \(firstName), Last Name = \(lastName)")
}
})
This will print every key "Id" and all the info
Thank You in advance :)

Answer 1

Since you have childByAutoId you have to use query ordered and query equal.
let reference = Database.database().reference().child("User_Informations").queryOrdered(byChild: "email")
reference.queryEqual(toValue: "ali_y_k#hotmail.com").observeSingleEvent(of: .childAdded) { (snapshot) in
let dictionary = snapshot.value as! [String : Any]
let firstName = dictionary["firstName"]
print(firstName)
}

Answer 2

You need to use the current user id after you login
let currentUserUid = FIRAuth.auth()!.currentUser!.uid
let databaseRef = Database.database().reference().child("User_Informations/\(currentUserUid)")
databaseRef.observeSingleEvent(of: .value, with: { (snapshot) in
}