Maximum Length UITextField

Question

When I tried How to set the maximum number of characters that can be entered into a UITextField using fast? , I saw that if I use all 10 characters, I also cannot erase the character.

The only thing I can do is cancel the operation (delete all characters together).

Does anyone know how not to lock the keyboard (so that I cannot add other letters / characters / numbers, but I can use backspace)?

Answer 1

In Swift 5 and iOS 12, try the following implementation of the textField(_:shouldChangeCharactersIn:replacementString:) method textField(_:shouldChangeCharactersIn:replacementString:) which is part of the UITextFieldDelegate protocol:

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { guard let textFieldText = textField.text, let rangeOfTextToReplace = Range(range, in: textFieldText) else { return false } let substringToReplace = textFieldText[rangeOfTextToReplace] let count = textFieldText.count - substringToReplace.count + string.count return count <= 10 } 

• The most important part of this code is the conversion of range ( NSRange ) to rangeOfTextToReplace ( Range<String.Index> ). Check out this video tutorial to see why this conversion is important.
• For this code to work correctly, you must also set the textField value smartInsertDeleteType to UITextSmartInsertDeleteType.no . This will prevent the possible insertion of (unwanted) extra space during the insert operation.

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The full code example below shows how to implement textField(_:shouldChangeCharactersIn:replacementString:) in a UIViewController :

 import UIKit class ViewController: UIViewController, UITextFieldDelegate { @IBOutlet var textField: UITextField! // Link this to a UITextField in Storyboard override func viewDidLoad() { super.viewDidLoad() textField.smartInsertDeleteType = UITextSmartInsertDeleteType.no textField.delegate = self } func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { guard let textFieldText = textField.text, let rangeOfTextToReplace = Range(range, in: textFieldText) else { return false } let substringToReplace = textFieldText[rangeOfTextToReplace] let count = textFieldText.count - substringToReplace.count + string.count return count <= 10 } } 

Answer 2

I do it like this:

 func checkMaxLength(textField: UITextField!, maxLength: Int) { if (countElements(textField.text!) > maxLength) { textField.deleteBackward() } } 

The code works for me. But I work with a storyboard. In the Storyboard, I add an action for the text field in the view controller in edit edited .

Answer 3

Update for Swift 4

  func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { guard let text = textField.text else { return true } let newLength = text.count + string.count - range.length return newLength <= 10 } 

Answer 4

Add more details from @Martin answer

 // linked your button here @IBAction func mobileTFChanged(sender: AnyObject) { checkMaxLength(sender as! UITextField, maxLength: 10) } // linked your button here @IBAction func citizenTFChanged(sender: AnyObject) { checkMaxLength(sender as! UITextField, maxLength: 13) } func checkMaxLength(textField: UITextField!, maxLength: Int) { // swift 1.0 //if (count(textField.text!) > maxLength) { // textField.deleteBackward() //} // swift 2.0 if (textField.text!.characters.count > maxLength) { textField.deleteBackward() } } 

Answer 5

In Swift 4

10 characters limit the text box and allow you to delete (return)

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { if textField == userNameFTF{ let char = string.cString(using: String.Encoding.utf8) let isBackSpace = strcmp(char, "\\b") if isBackSpace == -92 { return true } return textField.text!.count <= 9 } return true } 

Answer 6

 func checkMaxLength(textField: UITextField!, maxLength: Int) { if (textField.text!.characters.count > maxLength) { textField.deleteBackward() } } 

slight change for iOS 9

Answer 7

Swift 3

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { let nsString = NSString(string: textField.text!) let newText = nsString.replacingCharacters(in: range, with: string) return newText.characters.count <= limitCount } 

Answer 8

If you want to overwrite the last letter:

 let maxLength = 10 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { if range.location > maxLength - 1 { textField.text?.removeLast() } return true } 

Answer 9

I posted the solution using IBInspectable , so you can change the maximum length value both in the interface builder and programmatically. Check here

Answer 10

Beware of the UITextField undo error mentioned in this post: Set the maximum length of the UITextField character

here's how you fix it quick

 if(range.length + range.location > count(textField.text)) { return false; } 

Answer 11

 Here is my version of code. Hope it helps! func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { let invalidCharacters = NSCharacterSet(charactersInString: "0123456789").invertedSet if let range = string.rangeOfCharacterFromSet(invalidCharacters, options: nil, range:Range<String.Index>(start: string.startIndex, end: string.endIndex)) { return false } if (count(textField.text) > 10 && range.length == 0) { self.view.makeToast(message: "Amount entry is limited to ten digits", duration: 0.5, position: HRToastPositionCenter) return false } else { } return true } 

Answer 12

I use this protocol / extension in one of my applications and it is a little readable. I love the way it recognizes backspaces and explicitly tells you when a character is a backspace.

Some things to consider:

1. In any case, this protocol extension should indicate a character restriction. This will usually be your ViewController, but you can implement the character constraint as a computed property and return something else, such as a character limit on one of your models.

2. You will need to call this method inside your text box shouldChangeCharactersInRange delegate method. Otherwise, you cannot block text input by returning false, etc.

3. You probably want to allow reverse characters. . So I added an extra function to detect backspaces. Your shouldChangeCharacters method can verify this and return true at an early stage so that you always allow backspaces.

 protocol TextEntryCharacterLimited{ var characterLimit:Int { get } } extension TextEntryCharacterLimited{ func charactersInTextField(textField:UITextField, willNotExceedCharacterLimitWithReplacementString string:String, range:NSRange) -> Bool{ let startingLength = textField.text?.characters.count ?? 0 let lengthToAdd = string.characters.count let lengthToReplace = range.length let newLength = startingLength + lengthToAdd - lengthToReplace return newLength <= characterLimit } func stringIsBackspaceWith(string:String, inRange range:NSRange) -> Bool{ if range.length == 1 && string.characters.count == 0 { return true } return false } } 

If any of you are interested, I have a Github repository where I took some of these character behavior rules and put it on iOS. There, a protocol that you can implement to display the character limit on Twitter shows how much you went above the character limit.

CharacterLimited Framework on Github

Answer 13

Since delegates are 1 to 1 ratios, and I can use it elsewhere for other reasons, I like to limit the length of the text field by adding this code to my installation:

  required init(coder aDecoder: NSCoder) { super.init(coder: aDecoder)! setup() } required override init(frame: CGRect) { super.init(frame: frame) setup() } func setup() { // your setup... setMaxLength() } let maxLength = 10 private func setMaxLength() { addTarget(self, action: #selector(textfieldChanged(_:)), for: UIControlEvents.editingChanged) } @objc private func textfieldChanged(_ textField: UITextField) { guard let text = text else { return } let trimmed = text.characters.prefix(maxLength) self.text = String(trimmed) } 

Answer 14

You need to check if the existing row plus input is greater than 10.

  func textField(textField: UITextField!,shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool { NSUInteger newLength = textField.text.length + string.length - range.length; return !(newLength > 10) }