How to use TouchID using Swift? - ios

Question

The documentation that Apple has provided for TouchID implementation for iOS 8 is in Objective-C.
Is there a Swift version of it?
Objective-C:
- (IBAction)touchIDAvailable:(UIButton *)touchIDAvailableButton {
LAContext *context = [[LAContext alloc] init];
__block NSString *msg;
[context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:NSLocalizedString(#"Place your finger on the sensor", nil) reply: ^(BOOL success, NSError *authenticationError) {
if (success) {
}
}
}
Swift:
#IBAction func touchidbutton(sender: AnyObject) {
authContext.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: "Place your finger on the sensor"?, reply: ((success : Bool, NSError!) -> Void)?){
if (success) {
}
}
}

Answer 1

Here is my view controller that does these checks in Swift. While working on this I found the completion block/closure syntax in Swift to be very confusing.
Notice that some of the options changed in Beta 2 in order to give you more control over the Touch ID dialog such as disabling the fallback option or the cancel button.
// Imports
import UIKit
import LocalAuthentication
// Class Implementation
class FirstViewController: UIViewController {
// Class Properties
#IBOutlet var statusLabel : UILabel
#IBOutlet var headerString: UILabel
var authError : NSError?
var authContext = LAContext()
var statusText = ""
var alert = UIAlertController(title: "", message: "", preferredStyle: UIAlertControllerStyle.Alert)
// Class Methods
#IBAction func swiftButtonPress(sender : AnyObject) {
statusLabel.text = "Authenticating"
//Can we use local auth?
if authContext.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &authError) {
authContext.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics,
localizedReason: "I need to see if it's really you",
reply: {(success: Bool, error: NSError!) -> Void in
if success {
self.statusText = "Touch ID success!"
self.alert.title = "Success"
self.alert.message = "I knew it was you!"
} else {
self.statusText = "Touch ID failed!"
self.alert.title = "Failure"
switch error!.code {
case LAError.AuthenticationFailed.toRaw():
self.alert.message = "Authentication Failed"
case LAError.UserCancel.toRaw():
self.alert.message = "User canceled!"
case LAError.SystemCancel.toRaw():
self.alert.message = "The system canceled!"
case LAError.UserFallback.toRaw():
self.alert.message = "User request to enter passcode"
default:
self.alert.message = "Something else went wrong"
}
}
self.presentViewController(self.alert, animated: true, completion:{self.statusLabel.text = self.statusText})
})
} else {
self.statusText = "No local authentication"
alert.title = "Uh oh!"
switch authError!.code {
case LAError.TouchIDNotAvailable.toRaw():
alert.message = "No Touch ID on device"
case LAError.TouchIDNotEnrolled.toRaw():
alert.message = "No fingers enrolled"
case LAError.PasscodeNotSet.toRaw():
alert.message = "No passcode set"
default:
alert.message = "Something went wrong getting local auth"
}
self.presentViewController(self.alert, animated: true, completion: {self.statusLabel.text = self.statusText})
}
resetTouchID()
}
// Reset the system so we can go again
func resetTouchID() {
authContext = LAContext()
alert = UIAlertController(title: "", message: "", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Cancel, handler: nil))
let passcodeDetector = SwiftPasscodeDetector()
if passcodeDetector.checkForPasscode() {
headerString.text = "Passcode Set on Device"
} else {
headerString.text = "No Passcode Set"
}
}
// Inherited Methods
override func viewDidLoad() {
super.viewDidLoad()
resetTouchID()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 2

The API name is LAContext, and it's in the docs right here. It's pretty sparse, but it does its job. The method you probably want is
evaluatePolicy(_ policy: LAPolicy,
localizedReason localizedReason: String!,
reply reply: ((Bool, NSError!) -> Void)!)
The string argument is a subheader to display to the user, the reply is simply a callback block, and the policy currently has to be LAPolicy.DeviceOwnerAuthenticationWithBiometrics, but it appears the framework is there for other types of authentication in the future. Interesting...
Hope that helps! I tried on my phone because I was curious and it works wonderfully. Just make sure to query for ability to evaluate policy before you try to use it, in case it's on an older device.

Answer 3

The LAContext reference has method signatures in both Obj-C and Swift. Furthermore, if you ⌘-click on the LAContext class in your Swift code, you should be able to view the generated "header" for it in Swift.

Answer 4

Updated to Swift 3
static func authorizeWithTouchIDIfPossible(){
let authContext = LAContext()
var authError : NSError?
if authContext.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &authError) {
authContext.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "I need to see this", reply: { (success, error) in
if success {
print("Touch ID success!")
DispatchQueue.main.async {
//Do stuff here
}
} else {
print("Touch ID failed!")
}}
);
} else {
print("No local authentication")
}
}

Answer 5

Found it!
The link below is from a user named Shmoopi from Github. Shmoopi made the app to test the TouchID programmed in Swift.
https://github.com/Shmoopi/Swift-Touch-ID

Answer 6

Swift 3.0 in:
import UIKit
import LocalAuthentication
class ViewController: UIViewController
{
#IBAction func TouchBtn(_ sender: AnyObject)
{
let context:LAContext = LAContext()
if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error:nil)
{
context.evaluatePolicy(LAPolicy.deviceOwnerAuthenticationWithBiometrics, localizedReason:"We Need Your Id", reply:{
(wasSuccessful,Error) in
if wasSuccessful
{
print("Was a Sucess")
}
else
{
print("Not Logged In")
}
})
}
}
}

Answer 7

Swift 5 :
import LocalAuthentication
func authenticateUser() {
let context = LAContext()
var error: NSError?
if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
let reason = "Identify yourself!"
context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason) {
[unowned self] success, authenticationError in
DispatchQueue.main.async {
if success {
print("Success!")
} else {
let ac = UIAlertController(title: "Authentication failed", message: "Sorry!", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
self.present(ac, animated: true)
}
}
}
} else {
let ac = UIAlertController(title: "Touch ID not available", message: "Your device is not configured for Touch ID.", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
present(ac, animated: true)
}
}