Check that a input to UITextField is numeric only

Question

How do I validate the string input to a UITextField  I want to check that the string is numeric  including decimal points

User · Answer

pragma mark - UItextfield Delegate  -  BOOL textField  UITextField   textField shouldChangeCharactersInRange  NSRange range replacementString  NSString   string       if   string isEqualToString         string isEqualToString                  return TRUE             NSLog   Range    d    d  range length range location         NSRange  CURRANGE    NSString  rangeOfString string        if  range location    0  amp  amp  range length    0            if   string isEqualToString                      return TRUE                      return  self isNumeric string      - BOOL isNumeric  NSString  inputString      BOOL isValid   NO      NSCharacterSet  alphaNumbersSet    NSCharacterSet decimalDigitCharacterSet       NSCharacterSet  stringSet    NSCharacterSet characterSetWithCharactersInString inputString       isValid    alphaNumbersSet isSupersetOfSet stringSet       return isValid

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Not so elegant  but simple     -  BOOL  isNumber   NSString  input       return  input doubleValue     0     input isEqualToString   0       input isEqualToString   0 0

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This answer uses NSFormatter as said previously  Check it out    interface NSString  NSNumber  -  BOOL  isNumberWithLocale  NSLocale    stringLocale    -  BOOL  isNumber  -  NSNumber    getNumber   -  NSNumber    getNumberWithLocale  NSLocale   stringLocale   end   implementation NSString  NSNumber  -  BOOL  isNumberWithLocale  NSLocale    stringLocale       return  self getNumberWithLocale stringLocale     nil    -  BOOL  isNumber       return   self getNumber      nil    -  NSNumber    getNumber       NSLocale  l en     NSLocale alloc  initWithLocaleIdentifier    en US           return  self getNumberWithLocale   l en autorelease        -  NSNumber    getNumberWithLocale  NSLocale   stringLocale       NSNumberFormatter  formatter        NSNumberFormatter alloc   init   autorelease        formatter setLocale  stringLocale        return   formatter numberFromString self        end   I hope it helps someone

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I wanted a text field that only allowed integers   Here s what I ended up with  using info from here and elsewhere    Create integer number formatter  in UIApplicationDelegate so it can be reused     property  nonatomic  retain  NSNumberFormatter  integerNumberFormatter   -  BOOL application  UIApplication   application didFinishLaunchingWithOptions  NSDictionary   launchOptions          Create and configure an NSNumberFormatter for integers     integerNumberFormatter     NSNumberFormatter alloc  init        integerNumberFormatter setMaximumFractionDigits 0        return YES      Use filter in UITextFieldDelegate    interface MyTableViewController   UITableViewController  lt UITextFieldDelegate gt        ictAppDelegate  appDelegate     -  BOOL textField  UITextField   textField shouldChangeCharactersInRange  NSRange range replacementString  NSString   string          Make sure the proposed string is a number     NSNumberFormatter  inf    appDelegate integerNumberFormatter       NSString  proposedString    textField text stringByReplacingCharactersInRange range withString string       NSNumber  proposedNumber    inf numberFromString proposedString       if  proposedNumber               Make sure the proposed number is an integer         NSString  integerString    inf stringFromNumber proposedNumber           if   integerString isEqualToString proposedString                    proposed string is an integer             return YES                          Warn the user we re rejecting the change     AudioServicesPlayAlertSound kSystemSoundID Vibrate       return NO

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-  BOOL textField  UITextField   textField shouldChangeCharactersInRange  NSRange range replacementString  NSString   string       if string length  gt  0                NSCharacterSet  numbersOnly    NSCharacterSet characterSetWithCharactersInString   0123456789            NSCharacterSet  characterSetFromTextField    NSCharacterSet characterSetWithCharactersInString string            BOOL stringIsValid    numbersOnly isSupersetOfSet characterSetFromTextField           return stringIsValid            return YES

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For integer test it ll be   -  BOOL  isIntegerNumber   NSString  input       return  input integerValue     0     input isEqualToString   0

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You can do it in a few lines like this    BOOL valid  NSCharacterSet  alphaNums    NSCharacterSet decimalDigitCharacterSet   NSCharacterSet  inStringSet    NSCharacterSet characterSetWithCharactersInString myInputField text   valid    alphaNums isSupersetOfSet inStringSet       if   valid     Not numeric   -- this is for validating input is numeric chars only  Look at the documentation for NSCharacterSet for the other options  You can use characterSetWithCharactersInString to specify any set of valid input characters

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If you want a user to only be allowed to enter numerals  you can make your ViewController implement part of UITextFieldDelegate and define this method   -  BOOL textField  UITextField   textField shouldChangeCharactersInRange  NSRange range replacementString  NSString   string     NSString  resultingString    textField text stringByReplacingCharactersInRange  range withString  string         The user deleting all input is perfectly acceptable    if   resultingString length     0        return true         NSInteger holder     NSScanner  scan    NSScanner scannerWithString  resultingString      return  scan scanInteger   amp holder   amp  amp   scan isAtEnd       There are probably more efficient ways  but I find this a pretty convenient way  And the method should be readily adaptable to validating doubles or whatever  just use scanDouble  or similar

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Hi had the exact same problem and I don t see the answer I used posted  so here it is     I created and connected my text field via IB   When I connected it to my code via Control Drag  I chose Action  then selected the Editing Changed event   This triggers the method on each character entry   You can use a different event to suit   Afterwards  I used this simple code to replace the text   Note that I created my own character set to include the decimal period character and numbers   Basically separates the string on the invalid characters  then rejoins them with empty string   -  IBAction myTextFieldEditingChangedMethod  UITextField   sender           NSCharacterSet  validCharacterSet    NSCharacterSet characterSetWithCharactersInString    0123456789            NSCharacterSet  invalidCharacterSet   validCharacterSet invertedSet          sender text     sender text componentsSeparatedByCharactersInSet invalidCharacterSet  componentsJoinedByString           Credits  Remove all but numbers from NSString

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IMO the best way to accomplish your goal is to display a numeric keyboard rather than the normal keyboard   This restricts which keys are available to the user  This alleviates the need to do validation  and more importantly it prevents the user from making a mistake  The number pad is also much nicer for entering numbers because the keys are substantially larger   In interface builder select the UITextField  go to the Attributes Inspector and change the  Keyboard Type  to  Decimal Pad      That ll make the keyboard look like this     The only thing left to do is ensure the user doesn t enter in two decimal places   You can do this while they re editing  Add the following code to your view controller  This code removes a second decimal place as soon as it is entered   It appears to the user as if the 2nd decimal never appeared in the first place   -  void viewDidLoad      super viewDidLoad       self textField addTarget self                     action  selector textFieldDidChange              forControlEvents UIControlEventEditingChanged      -  void textFieldDidChange  UITextField   textField     NSString  text   textField text    NSRange range    text rangeOfString           if  range location    NSNotFound  amp  amp         text hasSuffix        amp  amp        range location     text length - 1              There s more than one decimal     textField text    text substringToIndex text length - 1

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import  NSString Extension h      interface NSString  Extension       -  BOOL  isAnEmail    -  BOOL  isNumeric        end   implementation NSString  Extension   -  BOOL  isNumeric               NSString  emailRegex      0-9             NSPredicate  emailTest    NSPredicate predicateWithFormat   SELF MATCHES      emailRegex            return  emailTest evaluateWithObject self              NSString  localDecimalSymbol     NSLocale currentLocale  objectForKey NSLocaleDecimalSeparator             NSMutableCharacterSet  decimalCharacterSet    NSMutableCharacterSet characterSetWithCharactersInString localDecimalSymbol              decimalCharacterSet formUnionWithCharacterSet  NSCharacterSet alphanumericCharacterSet                         NSCharacterSet  nonNumbers    decimalCharacterSet invertedSet             NSRange r    self rangeOfCharacterFromSet  nonNumbers                        if  r location    NSNotFound                               check to see how many times the decimal symbol appears in the string  It should only appear once for the number to be numeric                int numberOfOccurances     self componentsSeparatedByString localDecimalSymbol  count -1                return  numberOfOccurances  gt  1    NO   YES                        else return NO

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There are a few ways you could do this    Use NSNumberFormatter s numberFromString  method   This will return an NSNumber if it can parse the string correctly  or nil if it cannot  Use NSScanner Strip any non-numeric character and see if the string still matches Use a regular expression   IMO  using something like - NSString doubleValue  wouldn t be the best option because both   0 0  and   abc  will have a doubleValue of 0   The  value methods all return 0 if they re not able to convert the string properly  so it would be difficult to distinguish between a legitimate string of   0  and a non-valid string   Something like C s strtol function would have the same issue   I think using NSNumberFormatter would be the best option  since it takes locale into account  ie  the number   1 23  in Europe  versus   1 23  in the USA

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Old thread  but it s worth mentioning that Apple introduced NSRegularExpression in iOS 4 0   Taking the regular expression from Peter s response      Look for 0-n digits from start to finish NSRegularExpression  noFunnyStuff    NSRegularExpression regularExpressionWithPattern        0  1-9   d          d      options 0 error nil       There should be just one match if   noFunnyStuff numberOfMatchesInString  lt  theString  gt  options 0 range NSMakeRange 0   lt  theString  gt  length      1           Yay  digits      I suggest storing the NSRegularExpression instance somewhere

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Here are a few one-liners which combine Peter Lewis  answer above  Check that a input to UITextField is numeric only  with NSPredicates       define REGEX FOR NUMBERS         -       0  1-9   d          d           define REGEX FOR INTEGERS        -       0  1-9   d           define IS A NUMBER string    NSPredicate predicateWithFormat   SELF MATCHES      REGEX FOR NUMBERS  evaluateWithObject string       define IS AN INTEGER string    NSPredicate predicateWithFormat   SELF MATCHES      REGEX FOR INTEGERS  evaluateWithObject string

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Late to the game but here a handy little category I use that accounts for decimal places and the local symbol used for it  link to its gist here   interface NSString  Extension   -  BOOL  isAnEmail  -  BOOL  isNumeric    end   implementation NSString  Extension           Determines if the current string is a valid email address          return BOOL - True if the string is a valid email address       -  BOOL  isAnEmail       NSString  emailRegex      A-Z0-9a-z    -    A-Za-z0-9 -      A-Za-z  2 4        NSPredicate  emailTest    NSPredicate predicateWithFormat   SELF MATCHES      emailRegex        return  emailTest evaluateWithObject self              Determines if the current NSString is numeric or not  It also accounts for the localised  Germany for example use     instead of      decimal point and includes these as a valid number          return BOOL - True if the string is numeric       -  BOOL  isNumeric       NSString  localDecimalSymbol     NSLocale currentLocale  objectForKey NSLocaleDecimalSeparator       NSMutableCharacterSet  decimalCharacterSet    NSMutableCharacterSet characterSetWithCharactersInString localDecimalSymbol        decimalCharacterSet formUnionWithCharacterSet  NSCharacterSet alphanumericCharacterSet         NSCharacterSet  nonNumbers    decimalCharacterSet invertedSet       NSRange r    self rangeOfCharacterFromSet  nonNumbers        if  r location    NSNotFound                   check to see how many times the decimal symbol appears in the string  It should only appear once for the number to be numeric          int numberOfOccurances     self componentsSeparatedByString localDecimalSymbol  count -1          return  numberOfOccurances  gt  1    NO   YES            else return NO      end

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This covers  Decimal part control  including number of decimals allowed   copy paste control  international separators    Steps    Make sure your view controller inherits from UITextFieldDelegate  class MyViewController  UIViewController  UITextFieldDelegate      In viewDidLoad  set your control delegate to self   override func viewDidLoad         super viewDidLoad        yourTextField delegate   self   Implement the following method and update the  decsAllowed  constant with the desired amount of decimals or 0 if you want a natural number    Swift 4  func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool        let decsAllowed  Int   2     let candidateText   NSString string  textField text   replacingCharacters in  range  with  string      let decSeparator  String   NumberFormatter   decimalSeparator        let splitted   candidateText components separatedBy  decSeparator      let decSeparatorsFound   splitted count - 1     let decimalPart   decSeparatorsFound  gt  0   splitted last           let decimalPartCount   decimalPart characters count      let characterSet   NSMutableCharacterSet decimalDigit       if decsAllowed  gt  0  characterSet addCharacters in  decSeparator        let valid   characterSet isSuperset of  CharacterSet charactersIn  candidateText    amp  amp                  decSeparatorsFound  lt   1  amp  amp                  decsAllowed  gt   decimalPartCount      return valid     If afterwards you need to safely convert that string into a number  you can just use Double yourstring  or Int yourstring  type cast  or the more academic way   let formatter   NumberFormatter   let theNumber  NSNumber   formatter number from  yourTextField text

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In Swift 4   let formatString    12345  if let number   Decimal string formatString        print  String contains only number     else      print  String doesn t contains only number

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You can use the doubleValue of your string like  NSString  string   1 22   double a  string doubleValue     i think this will return a as 0 0 if the string is invalid  it might throw an exception  in which case you can just catch it  the docs say 0 0 tho   more info here

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Accept decimal values in text fields with single    dot working with iPad and iPhone in Swift 3     func textField   textField  UITextField  shouldChangeCharactersIn range  NSRange  replacementString string  String  - gt  Bool           let inverseSet   NSCharacterSet charactersIn  0123456789   inverted          let components   string components separatedBy  inverseSet           let filtered   components joined separator               if filtered    string               return true           else               if string                          let countdots   textField text  components separatedBy      count - 1                 if countdots    0                       return true                  else                      if countdots  gt  0  amp  amp  string                                  return false                       else                           return true                                                      else                  return false

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I use this code in my Mac app  the same or similar should work with the iPhone   It s based on the RegexKitLite regular expressions and turns the text red when its invalid   static bool TextIsValidValue  NSString  newText  double  amp value         bool result   false       if    newText isMatchedByRegex        0  1-9   d          d                   result   true          value    newText doubleValue             return result     -  IBAction  doTextChanged  id sender        double value      if   TextIsValidValue   i pause stringValue   value                i pause setTextColor  NSColor blackColor               do something with the value       else            i pause setTextColor  NSColor redColor

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property  strong  NSNumberFormatter  numberFormatter   property  strong  NSString  oldStringValue   -  void awakeFromNib       super awakeFromNib     self numberFormatter     NSNumberFormatter alloc  init     self oldStringValue   self stringValue     self setDelegate self      -  void controlTextDidChange  NSNotification   obj     NSNumber  number    self numberFormatter numberFromString self stringValue     if  number        self oldStringValue   self stringValue      else       self stringValue   self oldStringValue

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To be more international  and not only US colored  -    just replace in the code above by  - NSNumber    getNumber     NSString  localeIdentifier     NSLocale autoupdatingCurrentLocale  localeIdentifier     NSLocale  l en     NSLocale alloc  initWithLocaleIdentifier  localeIdentifier      return  self getNumberWithLocale   l en autorelease

[objective-c] Check that a input to UITextField is numeric only

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