AppDelegate.swift

import UIKit
import RealmSwift
import TTTabBar

let realm = try! Realm()
let octoClient = OctolyClient(
    baseUrl: "https://www.octoly.com/api",
    apiVersion: "v1")

var currentUser:User? = realm.objects(User).first;

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window:UIWindow? = UIWindow(frame: UIScreen.mainScreen().bounds)

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        if let window = window {
            if (currentUser != nil) {
                window.rootViewController = TabBar()
                
            } else {
                let navcontroller = UINavigationController()
                navcontroller.viewControllers = [SignInController()]
                window.rootViewController = navcontroller
            }
            
            window.backgroundColor = TOPBAR_BACKGROUND_COLOR
            window.makeKeyAndVisible()
        }

        return true
    }
  }

SignInController.swift

import UIKit
import SwiftHTTP

class SignInController:UIViewController, UITextFieldDelegate {

    func connectToOctoly() {
        /* ... */
        let params = ["email": (self.emailField?.text)!, "password": (self.passwordField?.text)!]
        octoClient.post("/session", options: params) {
            json in
            let responseData = json as! NSDictionary

            currentUser = User()

            if let token = responseData["private_token"] as? String {
                currentUser?.privateToken = token
                octoClient.setToken(token)
            }

            if let first_name = responseData["first_name"] as? String {
                currentUser?.firstName = first_name
            }

            if let last_name = responseData["last_name"] as? String {
                currentUser?.lastName = last_name
            }
            
            try! realm.write {
                realm.add(currentUser!)
            }
        }
    }
}