LAContext canEvaluatePolicy and Swift 2 - ios

Question

This is my code in Swift:
if (LAContext().canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics)) {
return true;
}
With Swift2 I changed my code to look like this:
if #available(iOS 8, *) {
if (LAContext().canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics)) {
return true;
}
}
But I get the following error:
Call can throw, but it is not marked with 'try' and the error is not handled
What Am I doing wrong?

Answer 1

You need to do something like this:
do {
try laContext.canEvaluatePolicy(.DeviceOwnerAuthenticationWithBiometrics)
// Call evaluatePolicy here
} catch {
print("Cannot evaluate policy, error: \(error)")
}
All methods that returned a Bool and had an inout NSError? as the last parameter were automatically converted (Swift 2) to throw the error, so the parameter was removed. Also the Bool was redundant because it was equal to whether the inout NSError? is nil
EDIT: To get more information about the error use this within the catch:
switch LAError(rawValue: error.code)! {
case .AuthenticationFailed:
break
case .UserCancel:
break
case .UserFallback:
break
case .SystemCancel:
break
case .PasscodeNotSet:
break
case .TouchIDNotEnrolled:
break
default:
break
}
(You can look at all the possible errors by CMD clicking on LAError
EDIT: In XCode 7 beta 5/6 this method doesn't throw anymore, but takes an NSErrorPointer as the last parameter (as does NSURL's checkResourceIsReachableAndReturnError for reasons not known to me). You can however extend your LAContext to make a throwing method like before if you like:
extension LAContext {
func canEvaluatePolicyThrowing(policy: LAPolicy) throws {
var error : NSError?
canEvaluatePolicy(policy, error: &error)
if let error = error { throw error }
}
}

Answer 2

Try this code:
do {
try touchIDContext.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics)
//Comprobar la repuesta de esa autentificacion
touchIDContext.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: mensaje, reply: { (success, ErrorType) -> Void in
if success
{
// Autentificacion correcta
alert.title = "Genial!"
alert.message = "Te has autentificado correctamente"
// Mostramos este Alerview
self.presentViewController(alert, animated: true, completion: nil)
}
else
{
//AUTENTIFICACION FALLIDA
//PASAMOS VALORES AL ALERTVIEW
alert.title = "AUTENTIFICACION FALLIDA!!"
//OFRECEMOS MAS INFORMACION SOBRE EL FALLO DE AUTENTIFICAICON
switch ErrorType!.code {
case LAError.UserCancel.rawValue: alert.message = "Usuario Cancela"
case LAError.AuthenticationFailed.rawValue: alert.message = "Autentificacion Fallida!"
case LAError.PasscodeNotSet.rawValue: alert.message = "Password no configurado"
case LAError.SystemCancel.rawValue: alert.message = "Error de sistema"
case LAError.UserFallback.rawValue:alert.message = "Usuario selecciona contrasen"
default:alert.message = "Imposible Autentificarse"
}
//Mostramos el AlertView
self.presentViewController(alert, animated: true, completion: nil)
}
}) // cierre del clousure
} // cierre del do
catch {
print("Cannot evaluate policy, error: \(error)")
} // cierre del catch

Answer 3

For Swift 3, I do this:
context.evaluatePolicy(policy, localizedReason: ...) { (success: Bool, error: Error?) in
DispatchQueue.main.async {
if success {
...
} else if let error = error as? LAError {
switch error.code {
case LAError.authenticationFailed:
...
}
}
}
}