A simple tutorial that how to use Apple fingerprint authentication in your iOS8apps on iPhone 5S and plus.

What you need:

• iOS 8.0+
• iPhone 5S or superior
• LocalAuthentication.framework
• XCode 6+

Intro

With iOS8, Apple introduced a new framework, called LocalAuthentication that is used to authenticate users on devices.

At this moment, the only one allowed authentication is

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]LAPolicyDeviceOwnerAuthenticationWithBiometrics[/code]

as is shown in LocalAuthentication.framework/LAContext.h

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]typedef NS_ENUM(NSInteger, LAPolicy)
{
/// Device owner was authenticated using a biometric method.
/// @discussion Biometrics (Touch ID) authentication is required. If Touch ID is not available or
///             not enabled, policy evaluation will fail.
///             Touch ID authentication dialog contains a cancel button and a fallback button with
///             default title "Enter Password" which can be customized using localizedFallbackTitle
///             property.
LAPolicyDeviceOwnerAuthenticationWithBiometrics NS_ENUM_AVAILABLE(NA, 8_0) = kLAPolicyDeviceOwnerAuthenticationWithBiometrics
}NS_ENUM_AVAILABLE(10_10, 8_0);[/code]

…surely in the future this ENUM grows up!

Implementation

It’s very easy to use in app the Biometrics authentication.
First of all, import the required framework:

Next,
in your controller add the framework import:

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]#import <Localauthentication/LocalAuthentication.h>[/code]

Bla bla bla, ok, but I want to copy some code!

Create the LAContext class

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]LAContext *_context;
// […]
_context = [[LAContext alloc] init];[/code]

next, check if the device is allowed or support bio authentication:

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]- (BOOL) canUseBiometrics
{
return [_context canEvaluatePolicy: LAPolicyDeviceOwnerAuthenticationWithBiometrics error:nil];
}[/code]

and call performAuthentication method when you want:

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]- (void) performAuthentication
{
if ( ![self canUseBiometrics] ) return;

/*
Validate and verify a Touch ID fingerprint.
*/
[_context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics
localizedReason:@"Authenticate for server login"
reply:^(BOOL success, NSError *authenticationError)
{
if ( success ) {
NSLog(@"User is authenticated successfully");
} else {
switch ( authenticationError.code ) {
case LAErrorAuthenticationFailed:
NSLog(@"Authentication Failed");
break;
case LAErrorUserCancel:
NSLog(@"User pressed Cancel button");
break;
case LAErrorUserFallback:
[self showPasswordAlert];
break;
}
}
}];
}[/code]

Well done!

If you want to use “passcode” as showed in popup,

you should recognize the LAErrorUserFallback error, and add an UIAlertViewof type UIAlertViewStyleSecureTextInput and in his delegate, use the entered password as you like:

[code autolinks=”false” collapse=”false” firstline=”1″ gutter=”true” htmlscript=”false” light=”false” padlinenumbers=”false” smarttabs=”true” tabsize=”4″ toolbar=”false”]- (void) showPasswordAlert
{
UIAlertView *passwordAlert = [[UIAlertView alloc]
initWithTitle:@"Demo"
message:@"Please type your password"
delegate:self
cancelButtonTitle:@"Cancel"
otherButtonTitles:@"Ok", nil];

[passwordAlert setAlertViewStyle:UIAlertViewStyleSecureTextInput];
[passwordAlert show];
}

– (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
if ( buttonIndex == 1 )
{
NSLog(@"%@", [alertView textFieldAtIndex:0].text );
}
}

[/code]
that’s all.

Enjoy!