How to handle touchID when loading app from background Swift - ios

Question

I'm implementing the login possibility with touchID using Swift.
Following: when the App is started, there is a login screen and a touchID popup - that's working fine. The problem occurs, when the app is loaded from background: I want the touchID popup appear over a login screen if a specific timespan hasn't been exceeded yet - but this time I want the touchID to go to the last shown view before the app entered background. (i.e. if the user wants to cancel the touchID, there is a login screen underneath where he then can authenticate via password, which leads him to the last shown view OR if the touchID authentication succeeded, the login screen should be dismissed and the last shown view presented.)
I really tried everything on my own, and searched for answers - nothing did help me. Here is my code:
override func viewDidLoad() {
super.viewDidLoad()
//notify when foreground or background have been entered -> in that case there are two methods that will be invoked: willEnterForeground and didEnterBackground
let notificationCenter = NSNotificationCenter.defaultCenter()
notificationCenter.addObserver(self, selector: "willEnterForeground", name:UIApplicationWillEnterForegroundNotification, object: nil)
notificationCenter.addObserver(self, selector: "didEnterBackground", name: UIApplicationDidEnterBackgroundNotification, object: nil)
password.secureTextEntry = true
if (username != nil) {
username.text = "bucketFit"
}
username.delegate = self
password.delegate = self
if let alreadyShown : AnyObject? = def.objectForKey("alreadyShown") {
if (alreadyShown == nil){
authenticateWithTouchID()
}
}
}
willEnterForeground:
func willEnterForeground() {
//save locally that the guide already logged in once and the application is just entering foreground
//the variable alreadyShown is used for presenting the touchID, see viewDidAppear method
def.setObject(true, forKey: "alreadyShown")
if let backgroundEntered : AnyObject? = def.objectForKey("backgroundEntered") {
let startTime = backgroundEntered as! NSDate
//number of seconds the app was in the background
let inactivityDuration = NSDate().timeIntervalSinceDate(startTime)
//if the app was longer than 3 minutes inactiv, ask the guide to input his password
if (inactivityDuration > 2) {
showLoginView()
} else {
def.removeObjectForKey("alreadyShown")
showLoginView()
}
}
}
authenticateWithTouchID():
func authenticateWithTouchID() {
let context : LAContext = LAContext()
context.localizedFallbackTitle = ""
var error : NSError?
let myLocalizedReasonString : NSString = "Authentication is required"
//check whether the iphone has the touchID possibility at all
if context.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &error) {
//if yes then execute the touchID and see whether the finger print matches
context.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: myLocalizedReasonString as String, reply: { (success : Bool, evaluationError : NSError?) -> Void in
//touchID succeded -> go to students list page
if success {
NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in
self.performSegueWithIdentifier("studentsList", sender: self)
})
} else {
// Authentification failed
print(evaluationError?.description)
//print out the specific error
switch evaluationError!.code {
case LAError.SystemCancel.rawValue:
print("Authentication cancelled by the system")
case LAError.UserCancel.rawValue:
print("Authentication cancelled by the user")
default:
print("Authentication failed")
}
}
})
}
}
shouldPerformSegueWithIdentifier:
override func shouldPerformSegueWithIdentifier(identifier: String, sender: AnyObject?) -> Bool {
if (false) { //TODO -> username.text!.isEmpty || password.text!.isEmpty
notify("Login failed", message: "Please enter your username and password to proceed")
return false
} else if (false) { //TODO when backend ready! -> !login("bucketFit", password: "test")
notify("Incorrect username or password", message: "Please try again")
return false
//if the login page is loaded after background, dont proceed (then we need to present the last presented view on the stack before the app leaved to background)
} else if let alreadyShown : AnyObject? = def.objectForKey("alreadyShown") {
if (alreadyShown != nil){
//TODO check whether login data is correct
dismissLoginView()
return false
}
}
return true
}
Thank you in advance.

Answer 1

What you could do is create a AuthenticationManager. This manager would be a shared instance which keep track of whether authentication needs to be renewed. You may also want this to contain all of the auth methods.
class AuthenticationManager {
static let sharedInstance = AuthenticationManager()
var needsAuthentication = false
}
In AppDelegate:
func willEnterForeground() {
def.setObject(true, forKey: "alreadyShown")
if let backgroundEntered : AnyObject? = def.objectForKey("backgroundEntered") {
let startTime = backgroundEntered as! NSDate
//number of seconds the app was in the background
let inactivityDuration = NSDate().timeIntervalSinceDate(startTime)
//if the app was longer than 3 minutes inactiv, ask the guide to input his password
if (inactivityDuration > 2) {
AuthenticationManager.sharedInstance.needsAuthentication = true
}
}
}
Then, subclass UIViewController with a view controller named SecureViewController. Override viewDidLoad() in this subclass
override fun viewDidLoad() {
super.viewDidLoad()
if (AuthenticationManager.sharedInstance().needsAuthentication) {
// call authentication methods
}
}
Now, make all your View Controllers that require authentication subclasses of SecureViewController.