TiTouchId.h

//
//  TiTouchId.h
//  TiTouchId
//
//  Created by Hans Knöchel on 22.03.16.
//  Copyright © 2016 Hans Knoechel. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <LocalAuthentication/LocalAuthentication.h>

@interface TiTouchId : NSObject {
    LAContext *context;
}

- (BOOL)isSupported;

- (void)authenticateWithReason:(NSString*)reason andCallback:(void(^)(NSDictionary *attrs))callback;

@end

TiTouchId.m

#import "TiTouchId.h"
#import <UIKit/UIKit.h>

@implementation TiTouchId

-(instancetype)init
{
    if (self = [super init]) {
        context = [LAContext new];
    }
    
    return self;
}

-(BOOL)isSupported
{
    NSError *error;
    
    BOOL currentOSSupported = [[[UIDevice currentDevice] systemVersion] compare:@"8.0" options:NSNumericSearch] != NSOrderedAscending;
    BOOL touchIDSupported = [context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error];
    
    return currentOSSupported && touchIDSupported && !error;
}

-(void)authenticateWithReason:(NSString*)reason andCallback:(void(^)(NSDictionary *attrs))callback
{
    if (!reason || !callback) {
        NSLog(@"Ti.TouchID: Please provide a valid 'reason' and 'callback' parameter.");
        return;
    }
    
    [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:reason reply:^(BOOL success, NSError *error) {
        NSMutableDictionary *attrs = [@{@"success":[NSNumber numberWithBool:success]} mutableCopy];
        
        if (error) {
            [attrs setValue:[error localizedDescription] forKey:@"error"];
            [attrs setValue:[NSNumber numberWithInteger:[error code]] forKey:@"code"];
        }
        
        callback(attrs);
    }];

}

@end

ViewController.m

#import "TiTouchId.h"

TiTouchId *touchId = [TiTouchId new];
if ([touchId isSupported]) {
    [touchId authenticateWithReason:@"Please verify to continue" andCallback:^(NSDictionary *attrs) {
        BOOL success = [attrs valueForKey:@"success"];
        NSError *error = [attrs valueForKey:@"error"];
        
        NSLog(@"Success - %d", success);
        
        if (error) {
            NSLog(@"Error - %@", [error localizedDescription]);
            NSLog(@"Code - %lu", [error code]);
        }
    }];
} else {
    NSLog(@"Touch ID is not supported on this device");
}