Allow only Numbers for UITextField input

Question

The iPad does not have a "Numpad" keyboard like the iPhone/iPod does.

I'm looking to find how I can restrict the user's keyboard to only accept values 0 through 9.

I would imagine using UITextField's "shouldChangeCharactersInRange" but I don't know the best way to implement it.

Answer 1

This is how I handled the problem on a SSN verification field, you can modify the max length and remove the if statement checking for keyboard type if you need to.

There is also logic to suppress the max length alerts when the user is typing as opposed to pasting data.

In the context of this code, BasicAlert() is a #define macro that simply shows a UIAlertView or UIAlertController using the title and message strings passed.

// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the object that will contain this code, because otherwise it would never be called.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // allow backspace
    if (!string.length)
    {
        return YES;
    }

    // Prevent invalid character input, if keyboard is numberpad
    if (textField.keyboardType == UIKeyboardTypeNumberPad)
    {
        if ([string rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet].invertedSet].location != NSNotFound)
        {
            // BasicAlert(@"", @"This field accepts only numeric entries.");
            return NO;
        }
    }

    // verify max length has not been exceeded
    NSString *proposedText = [textField.text stringByReplacingCharactersInRange:range withString:string];

    if (proposedText.length > 4) // 4 was chosen for SSN verification
    {
        // suppress the max length message only when the user is typing
        // easy: pasted data has a length greater than 1; who copy/pastes one character?
        if (string.length > 1)
        {
            // BasicAlert(@"", @"This field accepts a maximum of 4 characters.");
        }

        return NO;
    }

    // only enable the OK/submit button if they have entered all numbers for the last four of their SSN (prevents early submissions/trips to authentication server)
    self.answerButton.enabled = (proposedText.length == 4);

    return YES;
}

Answer 2

You can use this code to allow only number in textField.

Before that set delegate for textField

      textFieldName.delegate=self;

or

      [textFieldName setDelegate:self];

Than use this code to allow only digit to textField

      - (BOOL) textField: (UITextField *)theTextField shouldChangeCharactersInRange:(NSRange)range replacementString: (NSString *)string {
//return yes or no after comparing the characters

      // allow backspace
      if (!string.length)
      {
           return YES;
      }

      ////for Decimal value start//////This code use use for allowing single decimal value
      //    if ([theTextField.text rangeOfString:@"."].location == NSNotFound)
      //    {
      //        if ([string isEqualToString:@"."]) {
      //            return YES;
      //        }
      //    }
      //    else
      //    {
      //        if ([[theTextField.text substringFromIndex:[theTextField.text rangeOfString:@"."].location] length]>2)   // this allow 2 digit after decimal 
      //        {
      //            return NO;
      //        }
      //    }
      ////for Decimal value End//////This code use use for allowing single decimal value

      // allow digit 0 to 9
      if ([string intValue])
      {
            return YES;
      }

      return NO;
    }

Answer 3

Try this to avoid textfield clearing issue

Swift 3.0

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    guard NSCharacterSet(charactersInString: "0123456789").isSupersetOfSet(NSCharacterSet(charactersInString: string)) else {
        return false
    }
    return true
}

Swift 4.0

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) else {
        return false
    }
    return true
}

Answer 4

Very specific steps for Swift code

You can provide logic that restricts the text field's input in the func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool method by implementing the UITextFieldDelegate protocol.

For the sake of clarity, these steps assume that your storyboard contains a View Controller with a text field object that should only accept digits.

1. Create a custom class for the view controller that extends UIViewController. Make sure that the scene in your storyboard refers to the custom class by setting the custom class value in Xcode's Identity Inspector.

   import UIKit
   class YourCustomController: UIViewController {
       override func viewDidLoad() {        
           super.viewDidLoad()
       }
   }
   

2. Create an outlet from your scene's text field to your custom View Controller.

   class YourCustomController: UIViewController {
       @IBOutlet weak var numberField: UITextField!
       ...
   }
   

3. Apply the UITextFieldDelegate protocol in your custom view controller.

   class YourCustomController: UIViewController, UITextFieldDelegate {
       ...
   }
   

4. In your custom view controller's viewDidLoad method, assign your text field's delegate to your custom view controller class.

   override func viewDidLoad() {        
       super.viewDidLoad()
       numberField.delegate = self
   }
   

5. Add the UITextFieldDelegate's func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool method.

   As a result of making your custom view controller the numberField's delegate in the previous step, this method will be called each time a user enters a character into the text field. If your method returns true then the character will remain in the text field. If your method returns false then the character will not remain in the text field.

   The string parameter is the character being entered by the user. If the string character can be converted to an Int then it is between 0 and 9; otherwise, it is some non-number character.

   class YourCustomController: UIViewController, UITextFieldDelegate {
       ...
       func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
   
           return Int(string) != nil
       }
   }
   

(See below for the full view controller code.)

---

Example View Controller with digits only text field

import UIKit

class YourCustomController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var numberField: UITextField!

    override func viewDidLoad() {        
        super.viewDidLoad()       
        numberField.delegate = self
    }

    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {        
        return Int(string) != nil
    }    
}

---

Example View Controller with a Decimal text field

If you want to support a decimal number then take advantage of NSNumberFormatter. See the code comments for the differences.

import UIKit

class YourCustomController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var numberField: UITextField!

    private var formatter: NSNumberFormatter!

    override func viewDidLoad() {        
        super.viewDidLoad()       
        numberField.delegate = self

        // Initialize the formatter; minimum value is set to zero; style is Decimal. 
        formatter = NSNumberFormatter()
        formatter.numberStyle = NSNumberFormatterStyle.DecimalStyle
        formatter.minimum = 0
    }

    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        // Combine the current text field value and the new string
        // character. If it conforms to the formatter's settings then
        // it is valid. If it doesn't then nil is returned and the
        // string character should not be allowed in the text field.         
        return formatter.numberFromString("\(textField.text)\(string)") != nil
    }    
}

Answer 5

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

    NSNumberFormatter * nf = [[NSNumberFormatter alloc] init];
    [nf setNumberStyle:NSNumberFormatterNoStyle];

    NSString * newString = [NSString stringWithFormat:@"%@%@",textField.text,string];
    NSNumber * number = [nf numberFromString:newString];

    if (number)
        return YES;
    else
       return NO;
}

Answer 6

I applied this and it works!!

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
// Check for non-numeric characters
NSUInteger lengthOfString = string.length;
for (NSInteger index = 0; index < lengthOfString; index++) {
    unichar character = [string characterAtIndex:index];
    if (character < 48) return NO; // 48 unichar for 0
    if (character > 57) return NO; // 57 unichar for 9
}
// Check total length for restrict user
NSUInteger proposedNewLength = textField.text.length - range.length + string.length;
if (proposedNewLength > 6)
    return YES;
return YES;                                                                                                                                     
}

Answer 7

NSString* val = [[textField text] stringByReplacingCharactersInRange:range withString:string];
    NSCharacterSet *allowedCharacterSet = [NSCharacterSet decimalDigitCharacterSet];
    if ([[string componentsSeparatedByCharactersInSet:[allowedCharacterSet invertedSet]] count] > 1 || [val length] > 5) {
        return NO;
    }

Answer 8

Works fine for me :

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (([string rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound) && !(range.length==1 && string.length==0)) {
            return NO;
        }
        return YES;
    }

Answer 9

Keep distinct presentation data from internal representation. There is a simpler way. Let NSNumberFormatter do the job:

 NSNumberFormatter* ns = [[NSNumberFormatter alloc] init];
 ns.numberStyle = NSNumberFormatterDecimalStyle;
 [ns setMaximumFractionDigits:2];
 // This is your internal representation of the localized number
 double a = [[ns numberFromString:self.textIVA.text] doubleValue]];

[mylabel setText:[NSString stringWithFormat:@"€ %@",
     [NSNumberFormatter localizedStringFromNumber:
                          [NSNumber numberWithDouble:a]
                                      numberStyle:NSNumberFormatterDecimalStyle]]];

Answer 10

If you use my specification pattern then code looks like this

textField.delegate = self

lazy var specification: Specification = {
    return RegularExpressionSpecification(pattern: "^(|0|[1-9]\\d{0,6})$")
}()

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let textFieldString: NSString = textField.text ?? ""
    let s = textFieldString.stringByReplacingCharactersInRange(range, withString:string)
    return specification.isSatisfiedBy(s)
}

func textFieldShouldReturn(textField: UITextField) -> Bool {
    let s = textField.text ?? ""
    let isTextValid = specification.isSatisfiedBy(s)
    if isTextValid {
        textField.resignFirstResponder()
    }
    return false
}

Answer 11

I have modified @iDev's answer to work for digitals and ".":

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
     // Check for non-numeric characters
     NSUInteger lengthOfString = string.length;
     for (NSInteger index = 0; index < lengthOfString; index++) {
         unichar character = [string characterAtIndex:index];
         if ((character < 48) && (character != 46)) return NO; 
         // 48 unichar for 0, and 46 unichar for point
         if (character > 57) return NO; 
         // 57 unichar for 9
     }
     // Check for total length
     NSUInteger proposedNewLength = textField.text.length - range.length + string.length;
     if (proposedNewLength > 6)
         return YES;
     return YES; 
 }

Answer 12

swift 3

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    if textField==yourTextFieldOutlet {
                if(CharacterSet.decimalDigits.isSuperset(of: CharacterSet(charactersIn: yourTextFieldOutlet.text!))){
//if numbers only, then your code here
                }
                else{
                showAlert(title: "Error",message: "Enter Number only",type: "failure")
                }
            }
    return true
    }

Answer 13

Use this code:

NSString* val = [[textField text] stringByReplacingCharactersInRange:range withString:string];
NSCharacterSet *allowedCharacterSet = [NSCharacterSet decimalDigitCharacterSet];
if ([[string componentsSeparatedByCharactersInSet:[allowedCharacterSet invertedSet]] count] > 1 || [val length] > 5) {
    return NO;
}