First attempt at porting FirebaseArray to swift - https://github.com/firebase/FirebaseUI-iOS

firebaseArray.swift

import XCPlayground
import Firebase
import PromiseKit

// MARK: FirebaseArrayDelegate

protocol FirebaseArrayDelegate: class  {
  func childNotFound(key: String)
  func childAdded(snapshot: FDataSnapshot, atIndex index: Int)
  func childChanged(snapshot: FDataSnapshot, atIndex index: Int)
  func childRemoved(snapshot: FDataSnapshot, atIndex index: Int)
  func childMoved(snapshot: FDataSnapshot, fromIndex: Int, toIndex: Int)
}

// MARK: FirebaseArray

class FirebaseArray {

  // MARK: properties

  weak var delegate: FirebaseArrayDelegate?

  // MARK: private properties

  private var snapshots: [FDataSnapshot] = []
  private let query: FQuery

  // MARK: initializers

  init(query: FQuery) {
    self.query = query
    initListeners()
  }

  // MARK: methods

  // MARK: Private methods
  private func indexForKey(key: String?) -> Int? {
    guard let key = key else { return -1 }
    for (index, snapshot) in snapshots.enumerate() where snapshot.key == key { return index }
    delegate?.childNotFound(key)
    return nil
  }

  private func initListeners() {
    query.observeEventType(.ChildAdded, andPreviousSiblingKeyWithBlock: {(snapshot, previousChildKey) in
      guard let previousIndex = self.indexForKey(previousChildKey) else { return }
      let index = previousIndex + 1

      self.snapshots.insert(snapshot, atIndex: index)
      self.delegate?.childAdded(snapshot, atIndex: index)
    })

    query.observeEventType(.ChildChanged, andPreviousSiblingKeyWithBlock: {(snapshot, previousChildKey) in
      guard let index = self.indexForKey(snapshot.key) else { return }
      self.snapshots[index] = snapshot
      self.delegate?.childChanged(snapshot, atIndex: index)
    })

    query.observeEventType(.ChildRemoved, withBlock: {(snapshot) in
      guard let index = self.indexForKey(snapshot.key) else { return }
      self.snapshots.removeAtIndex(index)
      self.delegate?.childRemoved(snapshot, atIndex: index)
    })

    query.observeEventType(.ChildMoved, andPreviousSiblingKeyWithBlock: {(snapshot, previousChildKey) in
      guard let fromIndex = self.indexForKey(snapshot.key) else { return }
      self.snapshots.removeAtIndex(fromIndex)

      guard let previousIndex = self.indexForKey(previousChildKey) else { return }
      let toIndex = previousIndex + 1
      self.snapshots.insert(snapshot, atIndex: toIndex)
      self.delegate?.childMoved(snapshot, fromIndex: fromIndex, toIndex: toIndex)
    })
  }
}

// MARK: FirebaseArray + CollectionType

extension FirebaseArray: CollectionType {
  typealias Index = Int
  typealias T = FDataSnapshot

  var startIndex: Int {
    return 0
  }

  var endIndex: Int {
    return snapshots.count
  }

  subscript(i: Int) -> T {
    return snapshots[i]
  }
}

// MARK: Reporter

class Reporter: FirebaseArrayDelegate {

  let array: FirebaseArray

  init(array: FirebaseArray) {
    self.array = array
    self.array.delegate = self
  }

  func childNotFound(key: String) {
    print("Key not found: \(key)")
  }

  func childAdded(snapshot: FDataSnapshot, atIndex index: Int) {
    print("\(snapshot.key) added at \(index)")
    print(array.map { $0.key })
    print("~~~~~")
  }

  func childChanged(snapshot: FDataSnapshot, atIndex index: Int) {
    print("\(snapshot.key) changed to \(index)")
    print(array.map { $0.key })
    print("~~~~~")
  }

  func childRemoved(snapshot: FDataSnapshot, atIndex index: Int) {
    print("\(snapshot.key) removed at \(index)")
    print(array.map { $0.key })
    print("~~~~~")
  }

  func childMoved(snapshot: FDataSnapshot, fromIndex: Int, toIndex: Int) {
    print("\(snapshot.key) moved from \(fromIndex) to \(toIndex)")
    print(array.map { $0.key })
    print("~~~~~")
  }
}

// MARK: Demo

func delay(time:Double, closure: () -> Void) {
  dispatch_after(
    dispatch_time(DISPATCH_TIME_NOW, Int64(time * Double(NSEC_PER_SEC))),
    dispatch_get_main_queue(), closure)
}


let ref = Firebase(url: "https://firenext-test2.firebaseio.com/")
ref.removeValue()

let array = FirebaseArray(query: ref.queryOrderedByPriority())
let reporter = Reporter(array: array)

delay(0.1) { ref.childByAppendingPath("a").setValue(true, andPriority: "a") }
delay(0.2) { ref.childByAppendingPath("c").setValue(true, andPriority: "c") }
delay(0.3) { ref.childByAppendingPath("b").setValue(true, andPriority: "b") }
delay(0.4) { ref.childByAppendingPath("c").setPriority("a") }
delay(0.5) { ref.childByAppendingPath("a").removeValue() }

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true