Searching through child values Firebase / Swift

Question

My database has values sorted like this :

 Users
    UID
      Username
      Email

I\'m wanting to implement a friend adding system where

Answer 1

Try this...

Assume a structure (this is Swift 2, Firebase 2)

users
  uid_0
    email: "someuser@thing.com"
    displayName: "some display name"

and we want to get uid_0's info

let displayName = "some display name"

usersRef.queryOrdered(byChild: "displayName").queryEqual(toValue: displayName)
              .observeSingleEvent(of: .childAdded) { (snapshot: FIRDataSnapshot) in {

     let dict = snapshot?.value as! [String: AnyObject]
     let email = dict["email"]
     let displayName = dict["displayName"]
     print(email!)
     print(displayName!)

     let key = snapshot?.key
     print(key!)
}

A couple things to note

The 'dict' variable is being told it's being assigned a dictionary of type [String: Anyobject].

Any Object could well, be any object. A String, another dictionary, an int. So you need to ensure you code can handle whatever the object is

The snapshot key in this case is the snapshot of this user, and the key must be the parent node, which in this case is uid_0. So the output is

someuser@thing.com
some display name
uid_0

EDIT:

Updated for Firebase 4, Swift 4 and handle the case where multiple children are returned

let usersRef = self.ref.child("users")

let input = "some display name"
let query = usersRef.queryOrdered(byChild: "displayName").queryEqual(toValue: input)
query.observeSingleEvent(of: .value, with: { snapshot in
    for child in snapshot.children {
        let snap = child as! DataSnapshot
        let dict = snap.value as! [String: Any]
        let email = dict["email"] as! String
        let displayName = dict["displayName"] as! String
        print(email)
        print(displayName)

        let key = snapshot.key
        print(key)
    }
})

Answer 2

When you execute a query against the Firebase Database, there will potentially be multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.

let query = REF_USERS.queryOrdered(byChild: "displayname").queryEqual(toValue: input)
query.observeSingleEvent(of: .value) { (snapshot: FIRDataSnapshot) in {
    for child in snapshot.children {
        print(child.key)
    }
}

Also see:

• Firebase snapshot.key not returning actual key?
• Firebase access keys in queryOrderBy
• Firebase access keys in queryOrderBy
• Firebase getting data in order