Firebase with Swift 3 counting the number of children

Question

I have an array of strings and I am trying to populate it through firebase. It is a chat application and when a user creates a room he or she names the room. When the user l

Answer 1

Firebase data is loaded (and synchronized) asynchronously. This is easiest to see if you add some debug logging:

let ref = firebase.child("users").child(fUID).child("participating")

print("Starting observing");
ref.observe(.value, with: { (snapshot: FIRDataSnapshot!) in
    print("Got snapshot");
    print(snapshot.childrenCount)
    rooms.count = snapshot.childrenCount
})

print("Returning count");
return rooms.count

When you run this snippet, the logging output will be:

Start observing

Returning count

Got snapshot

This is probably not the order you expected the output to be in. And it also explains why your count will never be correct: the data hasn't been loaded yet, so it can't be counted.

This is the reason why Firebase listeners work with callback blocks: the block is invoked when the data is synchronized.

Answer 2

I guess that "rooms" is an array of class Room.

"an error that count is a get only property" happen when you try to set the range of array "rooms" - You can't do that.

'count' properties is read-only access. In person language, It be like. You have a bag. You put a apple to the bag. You put another apple to the bag. Now you have 2 apple. You can't only say "My bag have 2 apples."

To fix it:

• You have to create variable with type 'Room' class for each snapshot : FIRDataSnapshot
• Add it to rooms.

Example:

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

let ref = firebase.child("users").child(fUID).child("participating")

ref.observe(.value, with: { (snapshot: FIRDataSnapshot!) in
    print(snapshot.childrenCount)

    let room = Room()
    // Use you snapshot(FIRDataSnapshot) to create the data of the room.
    rooms.append(room)
})

return rooms.count

}

Answer 3

My way is to have the closure. When the call has completed then it will return the number of children

typealias countAllPostsResult = (UInt) -> Void
class func countAllPosts(isDeleted: Bool,completedHandler: @escaping countAllPostsResult) {
    print("countAllPosts ...is running...", isDeleted)
    var dataSnapshot = [DataSnapshot]()

    Constants.Commons.posts_node_ref.queryOrdered(byChild: Constants.Posts.is_deleted).queryStarting(atValue: "false").queryEnding(atValue: "false\u{f8ff}").observeSingleEvent(of: .value, with: { (snapshot) -> Void in

        for snap in snapshot.children {
            dataSnapshot.append(snap as! DataSnapshot)
        }
        if dataSnapshot.count > 0 {
            completedHandler(UInt(dataSnapshot.count))
        } else {
            completedHandler(0)
        }
    })

}