问如何使用objective c访问我在UIAlertController中的文本字段的输入？

EN

if ([UIAlertController class]) {
            UIAlertController *alertControllerK2 = [UIAlertController
                                                    alertControllerWithTitle:@"\u00A0"
                                                    message:@"Please enter the first number."
                                                    preferredStyle:UIAlertControllerStyleAlert];
            UIAlertAction *K2okAction = [UIAlertAction
                                         actionWithTitle:@"OK"
                                         style:UIAlertActionStyleDefault
                                         handler:nil];
            [alertControllerK2 addTextFieldWithConfigurationHandler:^(UITextField *K2TextField)
             {
                 K2TextField.placeholder = NSLocalizedString(@"Please enter the first number.", @"Please enter the first number.");
             }];
            [alertControllerK2 addAction:K2okAction];
            [self presentViewController:alertControllerK2 animated:YES completion:nil];
        } else {
            UIAlertView *alertK2;
            alertK2 = [[UIAlertView alloc]
                       initWithTitle:@"\u00A0"
                       message:@"Please enter the first number."
                       delegate: self
                       cancelButtonTitle:@"OK"
                       otherButtonTitles:nil];
            alertK2.alertViewStyle=UIAlertViewStylePlainTextInput;
            [alertK2 show];
        }