Set the maximum character length of a UITextField in Swift

Question

I know there are other topics on this but I can t seem to find out how to implement it    I m trying to limit a UITextField to only 5 Characters   Preferably Alphanumeric and - and   and      I ve seen this code   func textField textField  UITextField  shouldChangeCharactersInRange range  NSRange                         replacementString string  String  - gt  Bool       let maxLength   4     let currentString  NSString   textField text     let newString  NSString                currentString stringByReplacingCharactersInRange range  withString  string      return newString length  lt   maxLength     and   func textField textField  UITextField  shouldChangeCharactersInRange range  NSRange  replacementString string  String  - gt  Bool        let length   count textField text utf16    count string utf16  - range length     return length  lt   10      I just don t know how to actually implement it or which  textfield  should I swap out for my custom named UITextField

User · Answer

I think extension is more handy for this  See full answer here  private var maxLengths    UITextField  Int        2 extension UITextField         3    IBInspectable var maxLength  Int       get            4       guard let length   maxLengths self  else           return Int max               return length           set         maxLengths self    newValue          5       addTarget          self          action   selector limitLength           forControlEvents  UIControlEvents EditingChanged                      func limitLength textField  UITextField           6     guard let prospectiveText   textField text       where prospectiveText characters count  gt  maxLength else           return            let selection   selectedTextRange        7     text   prospectiveText substringWithRange        Range lt String Index gt  prospectiveText startIndex    lt  prospectiveText startIndex advancedBy maxLength             selectedTextRange   selection

User · Answer

If you have multiple textField that have various length checks on one page I ve found an easy and short solution   class MultipleTextField  UIViewController        let MAX LENGTH TEXTFIELD A   10     let MAX LENGTH TEXTFIELD B   11      lazy var textFieldA  UITextField             let textField   UITextField           textField tag   MAX LENGTH TEXTFIELD A         textField delegate   self         return textField             lazy var textFieldB  UITextField             let textField   UITextField           textField tag   MAX LENGTH TEXTFIELD B         textField delegate   self         return textField            extension MultipleTextField  UITextFieldDelegate       func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool           return  range location  lt  textField tag   amp  amp   string count  lt  textField tag

User · Answer

Other solutions posted above produce a retain cycle due to the textfield map  Besides  the maxLength property should be nullable if not set instead of artificial Int max constructions  and the target will be set multiple times if maxLength is changed    Here an updated solution for Swift4 with a weak map to prevent memory leaks and the other fixes  private var maxLengths   NSMapTable lt UITextField  NSNumber gt  keyOptions  NSPointerFunctions Options weakMemory  valueOptions  NSPointerFunctions Options strongMemory   extension UITextField        var maxLength  Int            get               return maxLengths object forKey  self   intValue                   set               removeTarget self  action   selector limitLength   for   editingChanged              if let newValue   newValue                   maxLengths setObject NSNumber value  newValue   forKey  self                  addTarget self  action   selector limitLength   for   editingChanged                else                   maxLengths removeObject forKey  self                                      IBInspectable var maxLengthInspectable  Int           get               return maxLength    Int max                   set               maxLength   newValue                       objc private func limitLength   textField  UITextField            guard let maxLength   maxLength  let prospectiveText   textField text  prospectiveText count  gt  maxLength else               return                   let selection   selectedTextRange         text   String prospectiveText    lt prospectiveText index from  maxLength            selectedTextRange   selection

User · Answer

For Swift 5   Just write one line to set the max char length   self textField maxLength   10  For more details click here Credit  http   www swiftdevcenter com max-character-limit-of-uitextfield-and-allowed-characters-swift

User · Answer

My Swift 4 version of shouldChangeCharactersIn  func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange                 replacementString string  String  - gt  Bool            guard let preText   textField text as NSString               preText replacingCharacters in  range  with  string  count  lt   MAX TEXT LENGTH else               return false                    return true

User · Answer

This answer is for Swift 4  and is pretty straight forward with the ability to let backspace through   func textField   textField  UITextField                  shouldChangeCharactersIn range  NSRange                  replacementString string  String  - gt  Bool       return textField text  count  lt  10    string

User · Answer

I use this step  first Set delegate texfield in viewdidload       override func viewDidLoad             super viewDidLoad            textfield delegate   self          and then shouldChangeCharactersIn after you include UITextFieldDelegate   extension viewController  UITextFieldDelegate       func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool                   let newLength    textField text  utf16 count     string utf16 count - range length                 if newLength  lt   8                        return true                   else                       return false

User · Answer

TextField Limit Character After Block the Text  in Swift 4  func textField   textField  UITextField  shouldChangeCharactersIn range       NSRange replacementString string  String  - gt  Bool         if textField    self txtDescription           let maxLength   200         let currentString  NSString   textField text  as NSString         let newString  NSString   currentString replacingCharacters in  range  with  string  as NSString         return newString length  lt   maxLength            return true

User · Answer

update for this Fattie answer  thanks   extension UITextField            Runtime key     private struct AssociatedKeys               max lenght key         static var maxlength  UInt8   0             temp string key         static var tempString  UInt8   0                Limit the maximum input length of the textfiled      IBInspectable var maxLength  Int           get               return objc getAssociatedObject self   amp AssociatedKeys maxlength  as  Int    0                   set               objc setAssociatedObject self   amp AssociatedKeys maxlength  newValue  objc AssociationPolicy OBJC ASSOCIATION RETAIN NONATOMIC              addTarget self  action   selector handleEditingChanged textField     for   editingChanged                           temp string     private var tempString  String            get               return objc getAssociatedObject self   amp AssociatedKeys tempString  as  String                   set               objc setAssociatedObject self   amp AssociatedKeys tempString  newValue  objc AssociationPolicy OBJC ASSOCIATION RETAIN NONATOMIC                           When the text changes  process the amount of text in the input box so that its length is within the controllable range       objc private func handleEditingChanged textField  UITextField                 Special Processing for Chinese Input Method         guard markedTextRange    nil else   return            if textField text  count    maxLength                    SET lastQualifiedString where text length    max lenght             tempString   textField text           else if textField text  count    0  lt  maxLength                    clear lastQualifiedString when text lengeht  gt  maxlength             tempString   nil                        keep current text range in arcgives         let archivesEditRange  UITextRange           if textField text  count    0  gt  maxLength                    if text length  gt  maxlength remove last range to move to -1 postion              let position   textField position from  safeTextPosition selectedTextRange  start   offset  -1     textField endOfDocument             archivesEditRange   textField textRange from  safeTextPosition position   to  safeTextPosition position             else                    just set current select text range             archivesEditRange   selectedTextRange                        main handle string max length         textField text   tempString    String  textField text        prefix maxLength                last config edit text range         textField selectedTextRange   archivesEditRange                get safe textPosition     private func safeTextPosition   optionlTextPosition  UITextPosition   - gt  UITextPosition               beginningOfDocument - gt  The end of the the text document             return optionlTextPosition    endOfDocument

User · Answer

Here s a Swift 3 2  alternative that avoids unnecessary string manipulation  In this case  the maximum length is 10   func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool       let text   textField text            return text count - range length   string count  lt   10

User · Answer

I give a supplementary answer based on  Frouo   I think his answer is the most beautiful way  Becuase it s a common control we can reuse  And there is no leak problem here       private var kAssociationKeyMaxLength  Int   0      extension UITextField             IBInspectable var maxLength  Int               get                   if let length   objc getAssociatedObject self   amp kAssociationKeyMaxLength  as  Int                       return length                   else                       return Int max                                             set                   objc setAssociatedObject self   amp kAssociationKeyMaxLength  newValue   OBJC ASSOCIATION RETAIN                  self addTarget self  action   selector checkMaxLength   for   editingChanged                             The method is used to cancel the check when use Chinese Pinyin input method            Becuase the alphabet also appears in the textfield when inputting  we should cancel the check          func isInputMethod   - gt  Bool               if let positionRange   self markedTextRange                   if let     self position from  positionRange start  offset  0                        return true                                             return false                     func checkMaxLength textField  UITextField                 guard  self isInputMethod    let prospectiveText   self text                  prospectiveText count  gt  maxLength                 else                       return                            let selection   selectedTextRange             let maxCharIndex   prospectiveText index prospectiveText startIndex  offsetBy  maxLength              text   prospectiveText substring to  maxCharIndex              selectedTextRange   selection

User · Answer

Simple solution without using delegate   TEXT FIELD addTarget self  action   selector editingChanged sender     for   editingChanged     objc private func editingChanged sender  UITextField             if let text   sender text  text count  gt   MAX LENGHT               sender text   String text dropLast text count - MAX LENGHT               return

User · Answer

I have something to add to Aladin s answer    Your view controller should conform to UITextFieldDelegate  class MyViewController  UIViewController  UITextViewDelegate       Set the delegate of your textfield   To set the delegate  you can control drag from the textfield to your view controller in the storyboard   I think this is preferable to setting it in code Implement the method in your view controller   textField   shouldChangeCharactersInRange replacementString

User · Answer

1 Set the delegate of your textfield   textField delegate   self  2 Implement the method in your view controller      MARK  Text field delegate  extension ViewController  UITextFieldDelegate       func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool           return range location  lt  maxLength  maxLength can be any maximum length you can define

User · Answer

Your view controller should conform to UITextFieldDelegate  like below  class MyViewController  UIViewController  UITextFieldDelegate        Set the delegate of your textfield  myTextField delegate   self  Implement the method in your view controller   textField   shouldChangeCharactersInRange replacementString     All together  class MyViewController  UIViewController UITextFieldDelegate    set delegate to class    IBOutlet var mytextField  UITextField                 textfield variable   override func viewDidLoad         super viewDidLoad       mytextField delegate   self                    set delegate     func textField textField  UITextField  shouldChangeCharactersInRange range  NSRange                         replacementString string  String  - gt  Bool       let maxLength   4     let currentString  NSString   textField text     let newString  NSString                currentString stringByReplacingCharactersInRange range  withString  string      return newString length  lt   maxLength    For Swift 4 func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool       let maxLength   1     let currentString  NSString    textField text     quot  quot   as NSString     let newString  NSString           currentString replacingCharacters in  range  with  string  as NSString     return newString length  lt   maxLength    Allowing only a specified set of characters to be entered into a given text field func textField textField  UITextField  shouldChangeCharactersInRange range  NSRange  replacementString string  String  - gt  Bool     var result   true      if mytextField    numberField       if count string   gt  0         let disallowedCharacterSet   NSCharacterSet charactersInString   quot 0123456789 - quot   invertedSet       let replacementStringIsLegal   string rangeOfCharacterFromSet disallowedCharacterSet     nil       result   replacementStringIsLegal               return result    How to program an iOS text field that takes only numeric input with a maximum length

User · Answer

The same way Steven Schmatz did it but using Swift 3 0      max Length func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange                 replacementString string  String  - gt  Bool       let maxLength   4     let currentString  NSString   textField text  as NSString     let newString  NSString   currentString replacingCharacters in  range  with  string  as NSString     return newString length  lt   maxLength

User · Answer

Simply just check with the number of characters in the string    Add a delegate to view controller ans asign delegate       class YorsClassName   UITextFieldDelegate             check the number of chars allowed for textfield    func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool       if textField text  count    1           return false           return true     Note  Here I checked for only char allowed in textField

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Working In Swift4     STEP 1 set UITextFieldDelegate      class SignUPViewController  UIViewController   UITextFieldDelegate            IBOutlet weak var userMobileNoTextFiled  UITextField           override func viewDidLoad                 super viewDidLoad        STEP 2 set delegate                 userMobileNoTextFiled delegate   self                    set delegate                    func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool                 guard let text   userMobileNoTextFiled text else   return true                 let newLength   text count   string count - range length               return newLength  lt   10                  STEP 3 call func            func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool               let maxLength   10             set your need             let currentString  NSString   textField text  as NSString             let newString  NSString                   currentString replacingCharacters in  range  with  string  as NSString             return newString length  lt   maxLength

User · Answer

Just in case  don t forget to guard range size before applying it to the string  Otherwise  you will get crash if the user will do this   Type maximum length text Insert something  Nothing will be inserted due to length limitation  but iOS doesn t know about it  Undo insertion  You get crash  cause range will be greater than actual string size   Also  using iOS 13 users can accidentally trigger this by gestures  I suggest you add to your project this  extension String       func replace with text  String  in range  NSRange  - gt  String            guard range location   range length  lt   self count else   return nil           return  self as NSString  replacingCharacters in  range  with  text            And use it like this   func textView   textView  UITextView  shouldChangeTextIn range  NSRange  replacementText text  String  - gt  Bool       guard let newText   textView text replace with  text  in  range  else   return false       return newText count  lt  maxNumberOfCharacters     Otherwise  you will constantly be getting crashed in your app

User · Answer

Swift 4  simply use   public func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool       return range location  lt  10

User · Answer

Modern Swift Note that much of the example code online regarding this problem is extremely out of date  Paste the following into any Swift file in your project   You can name the file anything  for example   quot Handy swift quot    This finally fixes one of the stupidest problems in iOS   Your text fields now have a  maxLength  It is completely OK to set that value in storyboard during development  or  set it in code while the app is running     simply have this in any Swift file  say  Handy swift  import UIKit private var   maxLengths    UITextField  Int    extension UITextField        IBInspectable var maxLength  Int           get               guard let l     maxLengths self  else                  return 150     global default-limit  or just  Int max                            return l                   set                 maxLengths self    newValue             addTarget self  action   selector fix   for   editingChanged                      func fix textField  UITextField            let t   textField text         textField text   t  prefix maxLength  string          It s that simple   Footnote - these days to safely truncate a String in swift  you simply  prefix n   An even simpler one-off version    The above fixes all text fields in your project  If you just want one particular text field to simply be limited to say  quot 4 quot   and that s that    class PinCodeEntry  UITextField            override func didMoveToSuperview                      super didMoveToSuperview           addTarget self  action   selector fixMe   for   editingChanged                  objc private func fixMe     text   text  prefix 4       Phew  That s all there is to it   Just BTW  here s a similar very useful tip relating to UITextView  https   stackoverflow com a 42333832 294884    For the OCD programmer  like me     As  LeoDabus reminds   prefix returns a substring  If you re incredibly caring  this let t   textField text textField text   t  prefix maxLength   would be if let t  String   textField text       textField text   String t prefix maxLength      Enjoy

[ios] Set the maximum character length of a UITextField in Swift

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