Myujth

use this code if you don't want work with tag and it works better then above

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
 // On inputing value to textfield
 if ((textField.text?.characters.count)! < 1 && string.characters.count > 0)
 if(textField == txtOne)
 txtTwo.becomeFirstResponder()
 
 if(textField == txtTwo)
 txtThree.becomeFirstResponder()
 
 if(textField == txtThree)
 txtFour.becomeFirstResponder()
 
 textField.text = string
 return false

 else if ((textField.text?.characters.count)! >= 1 && string.characters.count == 0)
 // on deleting value from Textfield
 if(textField == txtTwo)
 txtOne.becomeFirstResponder()
 
 if(textField == txtThree)
 txtTwo.becomeFirstResponder()
 
 if(textField == txtFour) 
 txtThree.becomeFirstResponder()
 
 textField.text = ""
 return false
 else if ((textField.text?.characters.count)! >= 1 )
 textField.text = string
 return false
 
 return true
 

It can be achieve using UITextField delegate & by setting Tag for each Textfield in increasing order (say 1 - 4), below is the delegate handler to solve the issue.

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool 
 // On inputing value to textfield
 if (textField.text?.characters.count < 1 && string.characters.count > 0)
 let nextTag = textField.tag + 1;

 // get next responder
 var nextResponder = textField.superview?.viewWithTag(nextTag);

 if (nextResponder == nil)
 nextResponder = textField.superview?.viewWithTag(1);
 
 textField.text = string;
 nextResponder?.becomeFirstResponder();
 return false;
 
 else if (textField.text?.characters.count >= 1 && string.characters.count == 0)
 // on deleteing value from Textfield
 let previousTag = textField.tag - 1;

 // get next responder
 var previousResponder = textField.superview?.viewWithTag(previousTag);

 if (previousResponder == nil)
 previousResponder = textField.superview?.viewWithTag(1);
 
 textField.text = "";
 previousResponder?.becomeFirstResponder();
 return false;
 
 return true;
 

I have taken one Hidden text field & four imageViews for that with two images. One for Blank and other for Bullet same as iOS default.

Also set tags for four imageviews.

On Load set Focus for Pin Code

- (void)startPinCode

 txtPinCodeLockDigits.text = @"";

 for (int i = 1; i <= 4; i++) 

 UIImageView *img = (UIImageView *)[self.view viewWithTag:i];
 [img setImage:[UIImage imageNamed:@"Img_BG_PinCode.png"]];
 

 [txtPinCodeLockDigits becomeFirstResponder];

Then change imageview's images as per user input and only allow four characters

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

 NSString *result = [textField.text stringByReplacingCharactersInRange:range withString:string];
 textField.text = result;

 for (int i = 1; i <= 4; i++) 

 UIImageView *img = (UIImageView *)[self.view viewWithTag:i];
 if (i <= [result length])
 [img setImage:[UIImage imageNamed:@"Img_BG_PinCode_Filled.png"]];
 else
 [img setImage:[UIImage imageNamed:@"Img_BG_PinCode.png"]];
 

 NSLog(@"Result :: %@", result);

 if ([result length] == 4) 
 [self performSelector:@selector(keyGenerationForApplication:) withObject:result afterDelay:0.2];
 

 return NO;

After Four characters call function for generated PIN Code and store it in User Defaults same as iOS default PIN settings

- (void)keyGenerationForApplication:(NSString *)pinCode

 int appCode = [pinCode intValue];
 [DefaultsValues setIntegerValueToUserDefaults:appCode ForKey:PIN_LOCK_PATTERN];

Here, you can again call StartPinCode method for re-confirming code.

Hopefully, it'll help you.

Thanks

swift 2.3

 class BankDepositsWithOTPVC: UIViewController 

 let limitLength = 1 

 override func viewDidLoad() 
 super.viewDidLoad()
 


 

 // MARK: Textfield Validator

 extension BankDepositsWithOTPVC : UITextFieldDelegate 


 func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool 
 // On inputing value to textfield
 if (textField.text?.characters.count < 1 && string.characters.count > 0)
 let nextTag = textField.tag + 1;

 // get next responder
 let nextResponder = textField.superview?.viewWithTag(nextTag);

 if (nextResponder == nil)
 textField.resignFirstResponder()
 // nextResponder = textField.superview?.viewWithTag(1);
 
 textField.text = string;
 nextResponder?.becomeFirstResponder();
 return false;

 else if (textField.text?.characters.count >= 1 && string.characters.count > 0)
 // maximum 1 digit

textField.text = "";

 let nextTag = textField.tag + 1;

 // get next responder
 let nextResponder = textField.superview?.viewWithTag(nextTag);

 if (nextResponder == nil)
 textField.resignFirstResponder()
 // nextResponder = textField.superview?.viewWithTag(1);
 
 textField.text = string;
 nextResponder?.becomeFirstResponder();
 return false;
 
 else if (textField.text?.characters.count >= 1 && string.characters.count == 0)
 // on deleteing value from Textfield
 let previousTag = textField.tag - 1;

 // get next responder
 var previousResponder = textField.superview?.viewWithTag(previousTag);

 if (previousResponder == nil)
 previousResponder = textField.superview?.viewWithTag(1);
 
 textField.text = "";
 previousResponder?.becomeFirstResponder();
 return false;
 
 //return true;

 guard let text = textField.text else return true 
 let newLength = text.characters.count + string.characters.count - range.length
 return newLength <= limitLength

 

 

Objective-C

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

 if ((textField.text.length < 1) && (string.length > 0))
 

 NSInteger nextTag = textField.tag + 1;
 UIResponder* nextResponder = [textField.superview viewWithTag:nextTag];
 if (! nextResponder)
 [textField resignFirstResponder];
 
 textField.text = string;
 if (nextResponder)
 [nextResponder becomeFirstResponder];

 return NO;

 else if ((textField.text.length >= 1) && (string.length > 0))
 //FOR MAXIMUM 1 TEXT

 NSInteger nextTag = textField.tag + 1;
 UIResponder* nextResponder = [textField.superview viewWithTag:nextTag];
 if (! nextResponder)
 [textField resignFirstResponder];
 
 textField.text = string;
 if (nextResponder)
 [nextResponder becomeFirstResponder];

 return NO;
 
 else if ((textField.text.length >= 1) && (string.length == 0))
 // on deleteing value from Textfield

 NSInteger prevTag = textField.tag - 1;
 // Try to find prev responder
 UIResponder* prevResponder = [textField.superview viewWithTag:prevTag];
 if (! prevResponder)
 [textField resignFirstResponder];
 
 textField.text = string;
 if (prevResponder)
 // Found next responder, so set it.
 [prevResponder becomeFirstResponder];

 return NO;
 

 return YES;

Provide the tag to the textfield like 1,2,3,4 and directly use it

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool


 let next:NSInteger

 if string == "" 

 next = textField.tag - 1;

 
 else

 next = textField.tag + 1;

 

 if (textField.text?.characters.count)! >= 1 

 if textField.tag == 4 

 if string == "" 

 textField.text = ""

 let temptf = self.view.viewWithTag(next) as! UITextField

 temptf.becomeFirstResponder()

 return false

 
 else

 if (textField.text?.characters.count)! > 1 

 let stringg = textField.text!
 textField.text = stringg.replacingOccurrences(of: stringg, with: string)
 
 return false
 
 
 else
 if string == "" 

 textField.text = ""

 if next != 0 

 let temptf = self.view.viewWithTag(next) as! UITextField
 temptf.becomeFirstResponder()

 

 return false
 

 else

 if (textField.text?.characters.count)! > 1 


 let stringg = textField.text!
 textField.text = stringg.replacingOccurrences(of: stringg, with: string)

 

 let temptf = self.view.viewWithTag(next) as! UITextField

 temptf.becomeFirstResponder()

 
 
 

 return true

}

Try this
sample tutorial passcode lock

ViewController.h

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController<UITextFieldDelegate>

 IBOutlet UITextField *txtPassword;

 @end

ViewController.m

- (void)viewDidLoad

[super viewDidLoad];
txtPassword.delegate=self;



- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string 

NSUInteger newLength = [textField.text length] + [string length] - range.length;
return (newLength > 1) ? NO : YES;

Swift 4

Inspired by @Anurag Soni and @Varun Naharia answers

Variant A

extension EnterConfirmationCodeTextField: UITextFieldDelegate 

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
 guard let textFieldCount = textField.text?.count else return false 

 // Сlosure
 let setValueAndMoveForward = 
 textField.text = string
 let nextTag = textField.tag + 1
 if let nextResponder = textField.superview?.viewWithTag(nextTag) 
 nextResponder.becomeFirstResponder()
 
 

 // Сlosure
 let clearValueAndMoveBack = 
 textField.text = ""
 let previousTag = textField.tag - 1
 if let previousResponder = textField.superview?.viewWithTag(previousTag) 
 previousResponder.becomeFirstResponder()
 
 

 if textFieldCount < 1 && string.count > 0 

 setValueAndMoveForward()

 if textField.tag == 4 
 print("Do something")
 

 return false

 else if textFieldCount >= 1 && string.count == 0 

 clearValueAndMoveBack()
 return false

 else if textFieldCount >= 1 && string.count > 0 

 let nextTag = self.tag + 1
 if let previousResponder = self.superview?.viewWithTag(nextTag) 
 previousResponder.becomeFirstResponder()

 if let activeTextField = previousResponder as? UITextField 
 activeTextField.text = string
 
 

 return false
 

 return true

 

Variant B (a little bit another behavior):

extension EnterConfirmationCodeTextField: UITextFieldDelegate 

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
 guard let textFieldCount = textField.text?.count else return false 

 // Сlosure
 let setValueAndMoveForward = 
 textField.text = string
 let nextTag = textField.tag + 1
 if let nextResponder = textField.superview?.viewWithTag(nextTag) 
 nextResponder.becomeFirstResponder()
 
 

 // Сlosure
 let clearValueAndMoveBack = 
 textField.text = ""
 let previousTag = textField.tag - 1
 if let previousResponder = textField.superview?.viewWithTag(previousTag) 
 previousResponder.becomeFirstResponder()
 
 

 if textFieldCount < 1 && string.count > 0 

 setValueAndMoveForward()

 if textField.tag == 4 
 print("Do something")
 

 return false

 else if textFieldCount >= 1 && string.count == 0 

 clearValueAndMoveBack()
 return false

 else if textFieldCount >= 1 

 setValueAndMoveForward()
 return false
 

 return true

 

 

Also, I implemented this feature:

In the case where the last textFiled is empty, I just want to switch to the previous textFiled. I tried all this methods. But as for me the method below more elegant and works like a charm:

Variant A

class EnterConfirmationCodeTextField: UITextField 

 // MARK: Life cycle

 override func awakeFromNib() 
 super.awakeFromNib()

 delegate = self
 

 // MARK: Methods

 override func deleteBackward() 
 super.deleteBackward()

 let previousTag = self.tag - 1
 if let previousResponder = self.superview?.viewWithTag(previousTag) 
 previousResponder.becomeFirstResponder()

 if let activeTextField = previousResponder as? UITextField 
 if let isEmpty = activeTextField.text?.isEmpty, !isEmpty 
 activeTextField.text = String()
 
 
 
 

Variant B (a little bit another behavior):

class EnterConfirmationCodeTextField: UITextField 

 // MARK: Life cycle

 override func awakeFromNib() 
 super.awakeFromNib()

 delegate = self
 

 // MARK: Methods

 override func deleteBackward() 
 super.deleteBackward()

 let previousTag = self.tag - 1
 if let previousResponder = self.superview?.viewWithTag(previousTag) 
 previousResponder.becomeFirstResponder()
 
 

Assign EnterConfirmationCodeTextField for each of your textFields and set they appropriate tag value.

Swift 4

when you input a number from the pin code into a text field, you should let a number be shown and then the next text field will become the first responder, so change the first responder after the code was in the text view

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
 guard let textField = textField as? PinCodeTextField else return true 

 if string == "" // when the backward clicked, let it go :)
 return true
 

 // when textfield is not empty, well, next number
 if textField.pinCode.count == textField.maxCount 
 becomeFirstResponder(after: textField)
 return false
 

 if string.count > textField.maxCharacterCount // the max character count should be 1
 return false
 
 return true

// now the text field has been filled with a number
func textFieldCotentDidChange(_ textField: UITextField) 
 print("didchange")
 guard let textField = textField as? PinCodeTextField else return 
 if textField.pinCode.count == 0 
 becomeFirstResponder(before: textField)
 

 // when textfield has been filled, ok! next!
 if textField.pinCode.count == textField.maxCharacterCount 
 becomeFirstResponder(after: textField)
 

for more details and the simple demo, see this link

Just use TextFieldDelegate method and check the length of the TextField after every changes

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool 
 let newString = (textField.text! as NSString).stringByReplacingCharactersInRange(range, withString: string)
 if newString.characters.count == 1
 
 nextTextField.becomeFirstResponder()
 return true
 
 else
 
 return false
 

Modified Anurag Soni's answer in Swift 3.

• It assumes you have outlet collection named textFields and the text fields have ordered tags set


• It adds case when there's already some digit in text field and when user types something new - the digit is replaced


• Input is restricted to digits only


• 
  

  It prevents from pasting more than one digit

  
  
  

  func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
   // Restrict to only digits
   let aSet = NSCharacterSet(charactersIn:"0123456789").inverted
   let compSepByCharInSet = string.components(separatedBy: aSet)
   let numberFiltered = compSepByCharInSet.joined(separator: "")
  
   if string != numberFiltered 
   return false
   
  
   // Get the unwrapped text
   guard let text = textField.text else 
   return false
   
  
   if (text.characters.count < 1 && string.characters.count == 1) 
   // New value to empty text field
   textField.text = string
  
   // Next responder
   if let someTextField = (textFields.filter $0.tag == textField.tag + 1 ).first 
   someTextField.becomeFirstResponder()
   else 
   view.endEditing(true)
   
  
   return false
   else if (text.characters.count >= 1 && string.characters.count == 0)
   // On deleting value from Textfield
   textField.text = ""
  
   // Previous responder
   if let someTextField = (textFields.filter $0.tag == textField.tag - 1 ).first 
   someTextField.becomeFirstResponder()
   else 
   view.endEditing(true)
   
  
   return false
   else if string.characters.count == 1 
   // There's already some digit in text field
   // Replace it with new one
   textField.text = string
  
   // Next responder
   if let someTextField = (textFields.filter $0.tag == textField.tag + 1 ).first 
   someTextField.becomeFirstResponder()
   else 
   view.endEditing(true)
   
   
  
   return false
  
  

  
  

I was working on a similar functionality and did it in my way. Solution below.
Swift 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 

 //For clear button pressed
 //If the textfield has already text in it
 if string.count == 0 
 textField.text = string
 return true
 

 //For First time entry into the text field
 guard let text = textField.text, text.count <= 0 else 
 //If user enter second character
 return false
 
 //For First time entry into the text field
 if text.count == 0 
 textField.text = string
 textField.resignFirstResponder()
 self.nextResponde(tag: textField.tag)
 return true
 
 return false


//To make the next field as responder
func nextResponde(tag: Int) 
 switch tag 
 case self.PINTextField.tag:
 guard let text = self.PINTextField1.text, text.count == 1 else 
 self.PINTextField1.becomeFirstResponder()
 return
 
 case self.PINTextField1.tag:
 guard let text = self.PINTextField2.text, text.count == 1 else 
 self.PINTextField2.becomeFirstResponder()
 return
 
 case self.PINTextField2.tag:
 guard let text = self.PINTextField3.text, text.count == 1 else 
 self.PINTextField3.becomeFirstResponder()
 return
 
 default:
 let _ = tag
 

try this : - For swift 3.0

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool 
 // On inputing value to textfield
 if ((textField.text?.characters.count)! < 1 && string.characters.count > 0)
 let nextTag = textField.tag + 1;

 // get next responder
 let nextResponder = textField.superview?.viewWithTag(nextTag);
 textField.text = string;

 if (nextResponder == nil)
 textField.resignFirstResponder()
 
 nextResponder?.becomeFirstResponder();
 return false;
 
 else if ((textField.text?.characters.count)! >= 1 && string.characters.count == 0)
 // on deleting value from Textfield
 let previousTag = textField.tag - 1;

 // get next responder
 var previousResponder = textField.superview?.viewWithTag(previousTag);

 if (previousResponder == nil)
 previousResponder = textField.superview?.viewWithTag(1);
 
 textField.text = "";
 previousResponder?.becomeFirstResponder();
 return false;
 
 return true;

converted Anurag Soni answer in swift 3.0

You just have to implement this method only.