AWSMobileClient code for implementing basic auth or federated login using the AWS SDK for iOS and AWS Amplify Framework (CLI) - 2.7.0+

AuthViewController2.7.swift

//
//  AuthViewController.swift
//
//  Created by Hills, Dennis on 12/13/2018.
//  Copyright © 2018 Hills, Dennis. All rights reserved.
//
//  About: Using AWS Amplify Framework for iOS 2.7.0+ to implement Basic Auth via Cognito User Pools with example Facebook option
//         This sample includes the userState listener and AWSMobileClient implementation changes added to iOS SDK for AWS v.2.7.0+
//
//  AWS Amplify Documentation: https://aws-amplify.github.io/docs/ios/authentication
//  Basic Auth via User Pools blog: https://itnext.io/basic-authentication-for-ios-using-aws-amplify-and-amazon-cognito-233b943222d4
//  Facebook Login via Cognito Identity Pools (with User Pools, too): https://itnext.io/facebook-login-using-aws-amplify-and-amazon-cognito-4acf74875a04
//  Google Sign-In: https://itnext.io/google-sign-in-using-aws-amplify-and-amazon-cognito-69cc3bf219ad
//  Login with Amazon blog via Cognito Identity Pools only: https://itnext.io/federated-identities-using-login-with-amazon-with-amazon-cognito-and-aws-amplify-bfb7dfb7e185
//
//  # High level steps to implement Facebook auth into your iOS apps with AWS
//  [Prerequisites]
//  Create a basic single view controller iOS (Swift) Xcode project
//  Install & configure AWS Amplify Framework (CLI - https://aws-amplify.github.io): $ npm install -g @aws-amplify/cli

//  [Backend]
//  Amplify init (from Xcode project folder)
//  Amplify add auth (or Amplify update auth)
//  Amplify push

//  [Client]
//  Add AWSConfiguration.swift to your xcode project
//  Pod init
//  Add AWSMobileClient dependancies to Podfile
//  Pod install --repo-update
//  Add this code to your ViewController (No singleton required in the AppDelegate)
//  *NOTE* Make sure the ViewController has a NavigationController if you are using the Auth UI as part of the AWS SDK for iOS

import UIKit
import AWSMobileClient
import FBSDKLoginKit // FACEBOOK ONLY: Used for signing out of Facebook. FB SDK installed by AWS SDK for iOS

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        initializeAWSMobileClient() // Initialize the AWSMobileClient
    }
    
    // Initializing the AWSMobileClient and take action based on current user state
    func initializeAWSMobileClient() {
        AWSMobileClient.sharedInstance().initialize { (userState, error) in
            
            self.addUserStateListener() // Register for user state changes
            
            if let userState = userState {
                switch(userState){
                case .signedIn: // is Signed IN
                    print("Logged In")
                    print("Cognito Identity Id (authenticated): \(String(describing: AWSMobileClient.sharedInstance().identityId))")
                case .signedOut: // is Signed OUT
                    print("Logged Out")
                    print("Cognito Identity Id (unauthenticated): \(String(describing: AWSMobileClient.sharedInstance().identityId))")
                    DispatchQueue.main.async {
                        self.showSignIn()
                    }
                case .signedOutUserPoolsTokenInvalid: // User Pools refresh token INVALID
                    print("User Pools refresh token is invalid or expired.")
                    DispatchQueue.main.async {
                        self.showSignIn()
                    }
                case .signedOutFederatedTokensInvalid: // Login with Amazon, Facebook, Google, or Twitter refresh token INVALID
                    print("Federated refresh token is invalid or expired.")
                    DispatchQueue.main.async {
                        self.showSignIn()
                    }
                default:
                    AWSMobileClient.sharedInstance().signOut()
                }
            } else if let error = error {
                print(error.localizedDescription)
            }
        }
    }
    
    // Use the iOS SDK drop-in Auth UI to show login options to user (Basic auth, Google, or Facebook)
    // Note: The view controller implementing the drpo-in auth UI needs to be associated with a Navigation Controller.
    func showSignIn() {
        AWSMobileClient.sharedInstance().showSignIn(navigationController: self.navigationController!, {
            (userState, error) in
            if(error == nil){   // Successful signin
                DispatchQueue.main.async {
                    print("User successfully logged in")
                }
            }
        })
    }
    
    // AWSMobileClient - realtime notifications on user state changes
    // This is super useful for immediately taking action when a refresh token has expired or a user has logged out
    func addUserStateListener() {
        AWSMobileClient.sharedInstance().addUserStateListener(self) { (userState, info) in
            switch (userState) {
            case .guest:
                print("Listener: guest")
                print("Cognito Identity Id (unauthenticated): \(String(describing: AWSMobileClient.sharedInstance().identityId))")
            case .signedIn:
                print("Listener: signedIn") // Called after successful login with User Pools or Federated login via drop-in auth UI
                print("Cognito Identity Id (authenticated): \(String(describing: AWSMobileClient.sharedInstance().identityId))")
            case .signedOut:
                print("Listener: signedOut") // Triggered by AWSMobileClient.sharedInstance().signOut()
                print("Cognito Identity Id (authenticated): \(String(describing: AWSMobileClient.sharedInstance().identityId))")
            case .signedOutUserPoolsTokenInvalid:  // Cognito User Pools refresh token is invalid
                print("Listener: signedOutUserPoolsTokenInvalid")
            case .signedOutFederatedTokensInvalid: // Facebook, Google, Login with Amazon, or Twitter refresh token invalid
                print("Listener: signedOutFederatedTokensInvalid")

            default:
                print("unsupported userstate")
            }
        }
    }
   
    func signOut() {
        AWSMobileClient.sharedInstance().signOut()
        
        // FACEBOOK ONLY - Use to sign out the user from Facebook (good for testing or allowing the user to login as another FB user)
        let manager = FBSDKLoginManager()
        manager.logOut()
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        // Remove the AWSMobileClient user state listener when this VC goes away
        // AWSMobileClient.sharedInstance().removeUserStateListener(self)
    }
}