Don't allow A-Z and 0-9 number in textfield - ios

Question

I want to implement some validation in my project, validation is that: Don't allow number 0-9 and A-Z in UITextField, only allow GUJARATI letter in UITextField. I have tried some validation but It was not working. I need some help from anyone.
I have tried this below code:
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//limit the size :
if([self checkValidation:textField] == true)
{
return NO;
}
return YES;
}
- (BOOL)checkValidation:(UITextField *)textField
{
NSString *rejex = [NSString stringWithFormat:#"%#",#"[A-Za-z0-9]"];
NSPredicate *gujTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", rejex];
//if rejex fullfil than it will return true else false.
return [gujTest evaluateWithObject:textField.text];
}
TIA

Answer 1

In your checkValidation function, you are taking textField as an argument and extracting its text property - but you call it in shouldChangeCharactersInRange, and by that point the text property still holds the old value of text, before the update (it gets updated after you return true from this function). Do instead
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//limit the size :
if([self checkValidation:string] == true)
{
return NO;
}
return YES;
}
- (BOOL)checkValidation:(NSString *)string
{
let stringWithGujaratiCharacters = "અ" // string with all Gujarati letters
let characterSet = CharacterSet(charactersIn: stringWithGujaratiCharacters).inverted // character set containing every character besides Gujarati letters
return string.rangeOfCharacter(from: characterSet) != nil // returns true if string contains characters other than Gujarati letters
}
If you just don't want to allow latin alphanumeric characters, change your characterSet
let characterSet = CharacterSet.alphanumerics

Answer 2

Change textfield to string on below code. it will work.
if([self checkValidation:string] == true)
and
- (BOOL)checkValidation:(NSString *)textField
{
NSString *rejex = [NSString stringWithFormat:#"%#",#"[A-Za-z0-9]"];
NSPredicate *gujTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", rejex];
//if rejex fullfil than it will return true else false.
return [gujTest evaluateWithObject:textField];
}

Answer 3

For this problem it would be better to use a CharacterSet detection. Regular expression don't work very well with unicode. Also, it is better to check for characters your want to allow than the other way around:
let text = textField.text ?? ""
// https://unicode.org/charts/PDF/U0A80.pdf 0x0A80 ... 0x0AFF
let gurajatiCharacterSet = CharacterSet(charactersIn: Unicode.Scalar(0x0A80 as Int)! ... Unicode.Scalar(0x0AFF as Int)!)
return text.rangeOfCharacter(from: gurajatiCharacterSet.inverted) == nil
Objective-C:
NSUInteger minValue = 0x0A80;
NSUInteger maxValue = 0x0AFF;
NSCharacterSet *gurajatiCharacterSet = [NSCharacterSet characterSetWithRange:NSMakeRange(minValue, maxValue - minValue + 1)];
return [textField.text rangeOfCharacterFromSet:[gurajatiCharacterSet invertedSet]].location == NSNotFound;

Answer 4

For this problem you can use NSCharacterSet.
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSCharacterSet *myCharSet = [NSCharacterSet characterSetWithCharactersInString:#"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"];
for (int i = 0; i < [string length]; i++)
{
unichar c = [string characterAtIndex:i];
if (![myCharSet characterIsMember:c])
{
return NO;
}
}
return YES;
}