Allow only alphanumeric characters for a UITextField

问题:

How would I go about allowing inputting only alphanumeric characters in an iOS UITextField?

回答1:

Use the UITextFieldDelegate method -textField:shouldChangeCharactersInRange:replacementString: with an NSCharacterSet containing the inverse of the characters you want to allow. For example:

// in -init, -initWithNibName:bundle:, or similar NSCharacterSet *blockedCharacters = [[[NSCharacterSet alphanumericCharacterSet] invertedSet] retain];  - (BOOL)textField:(UITextField *)field shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)characters {     return ([characters rangeOfCharacterFromSet:blockedCharacters].location == NSNotFound); }  // in -dealloc [blockedCharacters release]; 

Note that you’ll need to declare that your class implements the protocol (i.e. @interface MyClass : SomeSuperclass ) and set the text field’s delegate to the instance of your class.

回答2:

This is how I do it:

// Define some constants: #define ALPHA                   @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" #define NUMERIC                 @"1234567890" #define ALPHA_NUMERIC           ALPHA NUMERIC  // Make sure you are the text fields 'delegate', then this will get called before text gets changed. - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {      // This will be the character set of characters I do not want in my text field.  Then if the replacement string contains any of the characters, return NO so that the text does not change.     NSCharacterSet *unacceptedInput = nil;      // I have 4 types of textFields in my view, each one needs to deny a specific set of characters:     if (textField == emailField) {         //  Validating an email address doesnt work 100% yet, but I am working on it....  The rest work great!         if ([[textField.text componentsSeparatedByString:@"@"] count] > 1) {             unacceptedInput = [[NSCharacterSet characterSetWithCharactersInString:[ALPHA_NUMERIC stringByAppendingString:@".-"]] invertedSet];         } else {             unacceptedInput = [[NSCharacterSet characterSetWithCharactersInString:[ALPHA_NUMERIC stringByAppendingString:@".!#$%&'*+-/=?^_`{|}~@"]] invertedSet];         }     } else if (textField == phoneField) {         unacceptedInput = [[NSCharacterSet characterSetWithCharactersInString:NUMERIC] invertedSet];     } else if (textField == fNameField || textField == lNameField) {         unacceptedInput = [[NSCharacterSet characterSetWithCharactersInString:ALPHA] invertedSet];     } else {         unacceptedInput = [[NSCharacterSet illegalCharacterSet] invertedSet];     }      // If there are any characters that I do not want in the text field, return NO.     return ([[string componentsSeparatedByCharactersInSet:unacceptedInput] count] 

Check out the UITextFieldDelegate Reference too.

回答3:

I found a simple and working answer and want to share:

connect your UITextField for the event EditingChanged to following IBAction

-(IBAction) editingChanged:(UITextField*)sender {         if (sender == yourTextField)     {         // allow only alphanumeric chars         NSString* newStr = [sender.text stringByTrimmingCharactersInSet:[[NSCharacterSet alphanumericCharacterSet] invertedSet]];          if ([newStr length] 

回答4:

Swift 3 version

Currently accepted answer approach:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {      // Get invalid characters     let invalidChars = NSCharacterSet.alphanumerics.inverted      // Attempt to find the range of invalid characters in the input string. This returns an optional.     let range = string.rangeOfCharacter(from: invalidChars)      if range != nil {         // We have found an invalid character, don't allow the change         return false     } else {         // No invalid character, allow the change         return true     } } 

Another equally functional approach:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {      // Get invalid characters     let invalidChars = NSCharacterSet.alphanumerics.inverted      // Make new string with invalid characters trimmed     let newString = string.trimmingCharacters(in: invalidChars)      if newString.characters.count 

回答5:

For Swift: Connect your UITextField for the event EditingChanged to following IBAction:

@IBAction func ActionChangeTextPassport(sender:UITextField){     if sender == txtPassportNum{         let newStr = sender.text?.stringByTrimmingCharactersInSet(NSCharacterSet.alphanumericCharacterSet().invertedSet)         if newStr?.characters.count 

回答6:

The RegEx way in Swift:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {      if string.isEmpty {          return true      }      let alphaNumericRegEx = "[a-zA-Z0-9]"      let predicate = NSPredicate(format:"SELF MATCHES %@", alphaNumericRegEx)      return predicate.evaluate(with: string) } 

回答7:

You will have to use the textField delegate methods, and use methods textFieldDidBeginEditing, shouldChangeCharactersInRange and textFieldDidEndEditing to check for the characters.

Please refer to this link for the documentation.

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