Require email textfield to have @ character

Question

When a user registers I need the email field to detect whether or not the field has a valid email in it (must have the @ symbol). How do I make the text field require this character in Swift? Such as Twitters signup.

https://twitter.com/signup

Answer 1

At first you need to use NSNotification to monitor the user's input. Red hint keeps showing

until user input some string likexxxx@xxx.com, the hint goes off. import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var emailTextField: UITextField!
    @IBOutlet weak var alertLabel: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        NSNotificationCenter.defaultCenter().addObserver(self, selector:"textFieldChanged:", name: UITextFieldTextDidChangeNotification, object: emailTextField)
        // Do any additional setup after loading the view, typically from a nib.
    }

    func textFieldChanged(sender:AnyObject) {
        var inputText = emailTextField.text
        var isValid = NSPredicate(format: "SELF MATCHES %@", "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}").evaluateWithObject(inputText)
        if(isValid == false){
            alertLabel.backgroundColor = UIColor.redColor()
            alertLabel.text = "Not a valid email address"
        }else {
            alertLabel.backgroundColor = UIColor.whiteColor()
            alertLabel.text = ""
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 2

I used textfield "Editing did End" method for validation when leave textfield.

-(BOOL)NSStringIsValidEmail:(NSString *)checkString
{
    BOOL stricterFilter = YES; 
    NSString *stricterFilterString = @"[A-Z0-9a-z\\._%+-]+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2,4}";
    NSString *laxString = @".+@([A-Za-z0-9]+\\.)+[A-Za-z]{2}[A-Za-z]*";
    NSString *emailRegex = stricterFilter ? stricterFilterString : laxString;
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
    return [emailTest evaluateWithObject:checkString];
}

-(IBAction)emailValidation:(id)sender
{

    if ([self NSStringIsValidEmail:self.emailTextField.text]) {
        NSLog(@"Successful= login");
    }
    else{
        UIAlertView *alrt=[[UIAlertView alloc] initWithTitle:@"Wrong Email" message:@"Please check your email " delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
        [alrt show];

    }

}

//Swift code

 @IBAction func emailValidation(sender: AnyObject) {

        if NSStringIsValidEmail(emailTextField.text) == true {
            println("Valid")
        //valid
        }
        else{
             println(" Not Valid")
            //invalid
        }

    }


    func NSStringIsValidEmail(checkString: NSString) ->Bool
    {

        var stricterFilter = true
        var stricterFilterString = "[A-Z0-9a-z\\._%+-]+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2,4}"
         var laxString = ".+@([A-Za-z0-9]+\\.)+[A-Za-z]{2}[A-Za-z]*"
        var  emailRegex = stricterFilter ? stricterFilterString : laxString

        var emailTest = NSPredicate(format:"SELF MATCHES %@" ,emailRegex)

        return emailTest.evaluateWithObject(checkString)
    }