Some firebase binding code

FirebaseValue.swift

//  FirebaseValue.swift
//  Created by Matt Seiler on 7/14/16.
//  Copyright © 2016 Matthew Seiler. All rights reserved.

import FitnetUtils
import FirebaseDatabase
import Foundation

class FirebaseValue<T>: Observable<T?> {

    private let ref: FIRDatabaseReference
    private let writeConverter: (T) -> AnyObject?
    private var handle: FIRDatabaseHandle?

    private var _value: T? {
        didSet {
            notify(_value)
        }
    }

    var value: T? {
        get {
            return _value
        }
        set {
            ref.setValue(newValue.ifSet(writeConverter))
        }
    }

    init(ref: FIRDatabaseReference, readConverter: (AnyObject) -> T?, writeConverter: (T) -> AnyObject?) {

        self.ref = ref
        self.writeConverter = writeConverter

        super.init()

        self.handle = ref.observeEventType(.Value, withBlock: { snap in
            let v = snap.value.ifSet(readConverter)
            self._value = v
        })
    }

    deinit {
        handle.ifSet(ref.removeObserverWithHandle)
    }

}

FirebaseValueReader.swift

//  FirebaseValueReader.swift
//  Created by Matt Seiler on 7/14/16.
//  Copyright © 2016 Matthew Seiler. All rights reserved.

import BrightFutures
import Foundation
import FirebaseDatabase

/**
 Reads a single value from firebase on-demand.
 (Not observable/dynamic in any way.)
 */
class FirebaseValueReader<T> {

    private let ref: FIRDatabaseQuery
    private let converter: (AnyObject) -> T?

    init(ref: FIRDatabaseQuery, converter: (AnyObject) -> T?) {
        self.ref = ref
        self.converter = converter
    }

    func read() -> Future<T?, NSError> {
        let p = Promise<T?, NSError>()

        ref.observeSingleEventOfType(
            .Value,
            withBlock: { snap in
                let r = snap.value.ifSet(self.converter)
                p.success(r)
            },
            withCancelBlock: { err in
                p.failure(err)
            }
        )

        return p.future
    }
}