networkingExample.swift

import Foundation

enum NMAdError: ErrorType , CustomStringConvertible {
  case NotConfigured(missing: String)
  case InvalidData(message: String)
  case NetworkingError(error: NSError)
  
  var description: String {
    switch self {
    case .InvalidData(let message):
      return "Invalid Data: \(message)"
    case .NotConfigured(let missing):
      return "Not Configured: Missing \(missing)"
    case .NetworkingError(let error):
      return "Networking Error: \(error.userInfo[NSLocalizedDescriptionKey])"
    }
  }
}

enum Result<SuccessObject, ErrorObject> {
  case Success(SuccessObject)
  case Failure(ErrorObject)
}

typealias NMAdSettingsRequestCompletion = (result: Result<NMAdSettings, NMAdError>) -> Void

class NMAdManager {

  static let sharedManager = NMAdManager()
  
  var settingsUrl: NSURL?
  
  func requestAdSettings(completion: NMAdSettingsRequestCompletion) {
    guard let settingsUrl = settingsUrl else {
      completion(result: Result.Failure(NMAdError.NotConfigured(missing: "Settings URL")))
      return
    }
    requestAdSettings(adSettingsUrl: settingsUrl, completion: completion)
  }
  
}

private extension NMAdManager {
  
  func requestAdSettings(adSettingsUrl adSettingsUrl: NSURL, completion: NMAdSettingsRequestCompletion) {
    let task = NSURLSession.sharedSession().dataTaskWithURL(adSettingsUrl) {
      (data, response, error) in
      
      if let error = error {
        completion(result: Result.Failure(NMAdError.NetworkingError(error: error)))
        return
      }
      
      guard let data = data else {
        completion(result: Result.Failure(NMAdError.InvalidData(message: "No data returned")))
        return
      }
      
      guard let adSettings = NMAdSettings.createWithData(data) else {
        completion(result: Result.Failure(NMAdError.InvalidData(message: "Could not convert data into expected class")))
        return
      }
      
      completion(result: Result.Success(adSettings))
    }
    
    task.resume()
  }
  
}

class ExampleAdRequester {
  
  var done: Bool?
  
  func requestSettings() {
    let adManager = NMAdManager()
    adManager.settingsUrl = NSURL(string: "https://s3.amazonaws.com/statictest.mobilelocalnews.com/settings/adsettings.json")!
    adManager.requestAdSettings { result in
      switch result {
      case let .Success(adSettings):
        print("Success: \(adSettings.globalAdSettings.appOpen?.enabled)")
      case let .Failure(error):
        switch error {
        case NMAdError.NotConfigured:
          print("\(error)")
          fatalError()
        case NMAdError.InvalidData(let message):
          print("Invalid Data: \(message)")
        case let e as NSError:
          print("NSError: \(e)")
        default:
          print("Unknown Failure: \(error)")
        }
      }
      
    }
  }
}