Brief introduction to fingerprint recognition in iOS development

//1. Determine whether the system version is greater than or equal to 8.0. If it is greater than or equal to or equal to, it means that fingerprint recognition can be used.  if([UIDevice currentDevice].>=8.0)
  {
  //The function of determining whether fingerprint recognition can be used can only be used after 5S   //Create the context of the LA object    LAContext * context = [[LAContext alloc]init];
    //Discern whether the device supports fingerprint recognition    //Evaluate means evaluation    //Policy means policy    // Used to check whether the touchID is available in the current device    if([context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:nil])
    {
   //LAPolicyDeviceOwnerAuthentication If we input the fingerprint three times wrong, a password box will pop up. If we do not enter the password.  You can also have two chances to verify your fingerprint if both    The system password box will continue to pop up for you to enter If you didn't entertouch IDWill be locked，andLAPolicyDeviceOwnerAuthenticationWithBiometricsThe input system will not pop up
    Password box，After three errors，No processing is done by default，We can also click on fingerprint recognition to enter，But if the input error is still done twicetouch idWill be locked
     //It means that fingerprint recognition technology can be used      [context evaluatePolicy:LAPolicyDeviceOwnerAuthentication localizedReason:@"Please verify your fingerprint to pay" reply:^
    (BOOL success, NSError * _Nullable error) {
        //It is executed in the child thread, so if you want to update the UI, you must return to the main thread to execute.        //Judge whether it is successful        if(success)
        {
          NSLog(@"%@",[NSThread currentThread]);
          NSLog(@"Verification Successfully");
        }
        else
        {
          NSLog(@"Verification failed");
        }
        NSLog(@"%@",[NSThread currentThread]);
        NSLog(@"%@",error);
        if(error)
        {
         if(==-2)
         {
         dispatch_async(dispatch_get_main_queue(), ^{
UIAlertController * vc = [UIAlertController alertControllerWithTitle:@"Fingerprint verification cancelled" message:@""
          preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction * action = [UIAlertAction actionWithTitle:@"confirm" style:UIAlertActionStyleDefault 
           handler:^(UIAlertAction * _Nonnull action) {
NSLog(@"---------");
}];
UIAlertAction * action1 = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel 
           handler:^(UIAlertAction * _Nonnull action) {
NSLog(@"hhhhhh");
}];
[vc addAction:action];
[vc addAction:action1];
[self presentViewController:vc animated:YES completion:nil];
});
         }
         else if(==-1)
         {
         dispatch_async(dispatch_get_main_queue(), ^{
UIAlertController * vc = [UIAlertController alertControllerWithTitle:@"The fingerprint has been misprinted 3 times" message:
            @"You have two more chances" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction * action = [UIAlertAction actionWithTitle:@"confirm" style:UIAlertActionStyleDefault 
            handler:^(UIAlertAction * _Nonnull action) {
NSLog(@"---------");
}];
[vc addAction:action];
[self presentViewController:vc animated:YES completion:nil];
});
         }
        }
      }];
    }
  }
  else
  {
    NSLog(@"Sorry, the system version is too low");
  }