UITextField text change event

Question

How can I detect any text changes in a textField  The delegate method shouldChangeCharactersInRange works for something  but it did not fulfill my need exactly  Since until it returns YES  the textField texts are not available to other observer methods    e g  in my code calculateAndUpdateTextFields did not get the updated text  the user has typed    Is their any way to get something like textChanged Java event handler    -  BOOL textField  UITextField   textField              shouldChangeCharactersInRange  NSRange range              replacementString  NSString   string        if  textField tag    kTextFieldTagSubtotal             textField tag    kTextFieldTagSubtotalDecimal            textField tag    kTextFieldTagShipping            textField tag    kTextFieldTagShippingDecimal                  self calculateAndUpdateTextFields               return YES

User · Answer

to set the event listener    self textField addTarget self action  selector textFieldDidChange   forControlEvents UIControlEventEditingChanged     to actually listen   -  void textFieldDidChange  UITextField   textField       NSLog   text changed       textField text

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Swift 3 1      Selector  ClassName MethodName     cell lblItem addTarget self  action   selector NewListScreen fieldChanged textfieldChange     for   editingChanged     func fieldChanged textfieldChange  UITextField

User · Answer

For Swift 3 0   let textField   UITextField    textField addTarget      nil      action   selector MyClass textChanged           for  UIControlEvents editingChanged     using class like   class MyClass       func textChanged sender  Any

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We can easily configure that from Storyboard  CTRL drag the  IBAction and change event as following

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From proper way to do uitextfield text change call back      I catch the characters sent to a UITextField control something like this       Add a  textFieldDidChange  notification method to the text field control    In Objective-C    textField addTarget self                action  selector textFieldDidChange        forControlEvents UIControlEventEditingChanged     In Swift   textField addTarget self  action   selector textFieldDidChange   for   editingChanged       Then in the textFieldDidChange method you can examine the contents of the textField  and reload your table view as needed    You could use that and put calculateAndUpdateTextFields as your selector

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Swift 4  func addNotificationObservers          NotificationCenter default addObserver self  selector   selector textFieldDidChangeAction       name   UITextFieldTextDidChange  object  nil       objc func textFieldDidChangeAction   notification  NSNotification         let textField   notification object as  UITextField     print textField text

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Swift 4 Version  Using Key-Value Observing Notify objects about changes to the properties of other objects   var textFieldObserver  NSKeyValueObservation   textFieldObserver   yourTextField observe   text  options    new   old      weak self   object  changeValue  in   guard let strongSelf   self else   return     print changeValue

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KVO solutions do not work   KVO does NOT work in iOS for controls   http   stackoverflow com a 6352525 1402846   https   developer apple com library archive documentation General Conceptual DevPedia-CocoaCore KVO html   In the observing class  you do this    Given that you know the text view you want to watch   var watchedTextView  UITextView    Do this   NotificationCenter default addObserver      self      selector   selector changed       name  UITextView textDidChangeNotification      object  watchedTextView    However  be careful with that    it s likely you only want to call that once  so do not call it in  for example  layoutSubviews it s quite difficult to know when to best call it during your bring-up process  It will depend on your situation  Unfortunately there is no standard  locked-in solution for example you usually certainly can not call it at init time  since of course watchedTextView may not exist yet        the next problem is that       None of the notifications are called when text is changed programmatically   This is a huge  age-old  and stupid  nuisance in iOS engineering   Controls simply do not - end of story - call the notifcations when the  text property is changed programmatically   This is insanely annoying because of course - obviously - every app ever made sets the text programmatically  such as clearing the field after the user posts  etc   You have to subclass the text view  or similar control  like this   class NonIdioticTextView  UIITextView        override var text  String               boilerplate code needed to make watchers work properly          get               return super text                   set               super text   newValue             NotificationCenter default post                  name  UITextView textDidChangeNotification                  object  self                         Tip - don t forget the super call has to come before   the post call    There is no solution available  unless  you fix the control by subclassing as shown just above  That is the only solution   Note that the notification  UITextView textDidChangeNotification   results in  func textViewDidChangeSelection   textView  UITextView     being called    Not textViewDidChange

User · Answer

Starting iOS 14 there is no need to make a selector  you can pass a UIAction with a closure instead  let editingChanged   UIAction     in        Do something when text changes      myTextField addAction editingChanged  for   editingChanged

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With closure      class TextFieldWithClosure  UITextField       var targetAction      - gt  Void             didSet               self addTarget self  action   selector self targetSelector   for   editingChanged                       func targetSelector             self targetAction                  and using  textField targetAction          will fire on text changed

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NSNotificationCenter defaultCenter  addObserver self  selector  selector didChangeTextViewText    name UITextFieldTextDidChangeNotification object nil      -  void  didChangeTextViewText      do something

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Swift 3 Version    class SomeClass  UIViewController  UITextFieldDelegate         IBOutlet weak var aTextField  UITextField        override func viewDidLoad             super viewDidLoad            aTextField delegate   self         aTextField addTarget self  action   selector SignUpVC textFieldDidChange   for  UIControlEvents editingChanged                    func textFieldDidChange   textField  UITextField              TEXT FIELD CHANGED  SECRET STUFF            Don t forget to set the delegate

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Here in swift version for same   textField addTarget self  action   textFieldDidChange    forControlEvents  UIControlEvents EditingChanged   func textFieldDidChange textField  UITextField         Thanks

User · Answer

You should use the notification to solve this problem because the other method will listen to the input box not the actually input especially when you use the Chinese input method  In viewDidload    NSNotificationCenter defaultCenter  addObserver self selector  selector textFiledEditChanged                                                    name   UITextFieldTextDidChangeNotification                                                 object youTarget     then   -  void textFiledEditChanged  NSNotification   obj   UITextField  textField    UITextField   obj object  NSString  toBestring   textField text  NSArray  currentar    UITextInputMode activeInputModes   UITextInputMode  currentMode    currentar firstObject   if   currentMode primaryLanguage isEqualToString   zh-Hans          UITextRange  selectedRange    textField markedTextRange       UITextPosition  position    textField positionFromPosition selectedRange start offset 0       if   position            if  toBestring length  gt  kMaxLength              textField text    toBestring          finally you run will done

User · Answer

As stated here  UITextField text change event  it seems that as of iOS 6  iOS 6 0 and 6 1 checked  it is not possible to fully detect changes in UITextField objects just by observing the UITextFieldTextDidChangeNotification    It seems that only those changes made directly by the built-in iOS keyboard are tracked now  This means that if you change your UITextField object just by invoking something like this  myUITextField text     any text   you won t be notified about any changes at all   I don t know if this is a bug or it is intended  Seems like a bug since I haven t found any reasonable explanation in documentation  This is also stated here  UITextField text change event   My  solution  to this is to actually post a notification by myself for every change I make to my UITextField  if that change is done without using the built-in iOS keyboard   Something like this   myUITextField text     I m updating my UITextField directly in code    NSNotification  myTextFieldUpdateNotification        NSNotification notificationWithName UITextFieldTextDidChangeNotification                   object myUITextField     NSNotificationCenter defaultCenter    postNotification myTextFieldUpdateNotification     This way you are 100  confident that you ll receive the same notification when you change the  text property of your UITextField object  either when you update it  manually  in your code or through the built-in iOS keyboard   It is important to consider that  since this is not a documented behavior  this approach may lead to 2 notifications received for the same change in your UITextField object  Depending on your needs  what you actually do when your UITextField text changes  this could be an inconvenience for you   A slightly different approach would be to post a custom notification  this is  with a custom name other than UITextFieldTextDidChangeNotification  if you actually need to know whether the notification was yours or  iOS-made     EDIT   I ve just found a different approach which I think could be better   This involves the Key-Value Observing  KVO  feature of Objective-C  http   developer apple com library ios  documentation cocoa conceptual KeyValueObserving KeyValueObserving html   apple ref doc uid 10000177-BCICJDHA    Basically  you register yourself as an observer of a property and if this property changes you get notified about it  The  principle  is quite similar to how NSNotificationCenter works  being the main advantage that this approach works automatically also as of iOS 6  without any special tweak like having to manually post notifications    For our UITextField-scenario this works just fine if you add this code to  for example  your UIViewController that contains the text field   static void  myContext    amp myContext   -  void viewDidLoad      super viewDidLoad        Observing changes to myUITextField text     myUITextField addObserver self forKeyPath   text      options NSKeyValueObservingOptionNew NSKeyValueObservingOptionOld      context myContext       -  void observeValueForKeyPath  NSString   keyPath ofObject  id object  change  NSDictionary   change context  void   context      if context    myContext          Here you get notified every time myUITextField s  text  property is updated     NSLog   New value     - Old value              change objectForKey NSKeyValueChangeNewKey          change objectForKey NSKeyValueChangeOldKey          else       super observeValueForKeyPath keyPath ofObject object        change change context context        Credit to this answer regarding  context  management  https   stackoverflow com a 12097161 2078512  Note  Seems like while you are in the process of editing a UITextField with the built-in iOS keyboard  the  text  property of the text field is not updated with every new letter typed removed  Instead  the text field object gets updated  as a whole  after you resign the first responder status of the text field

User · Answer

Swift Version tested     Somewhere in your UIViewController  like viewDidLoad          self textField addTarget          self           action   selector SearchViewController textFieldDidChange               forControlEvents  UIControlEvents EditingChanged     Parameters explained   self textField   - gt  A UITextField defined somewhere in your UIViewController self   - gt  UIViewController  textFieldDidChange       - gt  Can be named anyway you like  as long as it is defined in your UIViewController   Then add the method you created above in your UIViewController     Gets called everytime the text changes in the textfield  func textFieldDidChange textField  UITextField        print  Text changed      textField text

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One thing is you may have multiple UITextFields  So  give them a tag and then you can switch on the tags  Here s how to setup an observer in any class pretty much   private func setupTextFieldNotification         NotificationCenter default addObserver forName  UITextField textDidChangeNotification  object  nil  queue  OperationQueue main     notification  in         if let textField   notification object as  UITextField  textField tag    100  let text   textField text               print  line  text                     deinit       NotificationCenter default removeObserver self

User · Answer

Swift  yourTextfield addTarget self  action   selector textFieldDidChange textField     for   editingChanged   Then  implement the callback function   objc final private func textFieldDidChange textField  UITextField    print  quot Text changed quot

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XenElement s answer is spot on    The above can be done in interface builder too by right-clicking on the UITextField and dragging the  Editing Changed  send event to your subclass unit

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I resolved the issue changing the behavior of shouldChangeChractersInRange  If you return NO the changes won t be applied by iOS internally  instead you have the opportunity to change it manually and perform any actions after the changes   -  BOOL textField  UITextField   textField shouldChangeCharactersInRange  NSRange range replacementString  NSString   string         Replace the string manually in the textbox     textField text    textField text stringByReplacingCharactersInRange range withString string         perform any logic here now that you are sure the textbox text has changed      self didChangeTextInTextField textField       return NO    this make iOS not to perform any action

User · Answer

Swift 3 Version  yourTextField addTarget self  action   selector YourControllerName textChanges       for  UIControlEvents editingChanged    And get the changes in here  func textChanges   textField  UITextField        let text   textField text     your desired text here        Now do whatever you want      Hope it helps

User · Answer

SwiftUI If you are using the native SwiftUI TextField or just using the UIKit UITextField  here is how   you can observe for text changes like  SwiftUI 2 0 From iOS 14  macOS 11  or any other OS contains SwiftUI 2 0  there is a new modifier called  onChange that detects any change of the given state  struct ContentView  View        State var text  String    quot  quot       var body  some View           TextField  quot Enter text here quot   text   text               onChange of  text                    print  0     You can do anything due to the change here                     self autocomplete  0     like this                        SwiftUI 1 0 For older iOS and other SwiftUI 1 0 platforms  you can use onReceive with the help of the combine framework  import Combine   onReceive Just text          print  0     Note that you can use text publisher instead of Just text  but it returns the change instead of the entire value

[ios] UITextField text change event

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