validate alphanumeric value in UITextField - objective-c

Question

I want alphanumeric value in textfield.If user enter only character or number then sending massage.Even no special characters acceptable.
NSString *str = askIdTxt.text;
NSCharacterSet *alphanumericSet = [NSCharacterSet alphanumericCharacterSet];
NSCharacterSet *numberSet = [NSCharacterSet decimalDigitCharacterSet];
BOOL isAlphaNumericOnly = [[str stringByTrimmingCharactersInSet:alphanumericSet] isEqualToString:#""] && ! [[str stringByTrimmingCharactersInSet:numberSet] isEqualToString:#""];
if (isAlphaNumericOnly) {
NSLog(#"isAplhaNumericOnly: %#",(isAlphaNumericOnly? #"Yes":#"No"));
}
This is always returning true. I am not getting what is wrong in this.

Answer 1

How about using regular expression:
-(BOOL)isAlphaNumericOnly:(NSString *)input
{
NSString *alphaNum = #"[a-zA-Z0-9]+";
NSPredicate *regexTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", alphaNum];
return [regexTest evaluateWithObject:input];
}
and then use it
if([self isAlphaNumeric:str])
{
NSLog(#"IT IS ALPHA NUMERIC STRING");
}
edit
The same technique can be used to validate passwords, you need only better regex:
-(BOOL)isPasswordStrong:(NSString *)password {
/*
8-20 chars
at least one letter
at least one number OR special character
no more than 3 repeated characters
*/
NSString *strongPass= #"^(?!.*(.)\\1{3})((?=.*[\\d])(?=.*[A-Za-z])|(?=.*[^\\w\\d\\s])(?=.*[A-Za-z])).{8,20}$";;
NSPredicate *regexTest = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", strongPass];
return [regexTest evaluateWithObject:password];
}
using the regular expression you can create different rules but this can give you a headstart,

Answer 2

Call this Method and modify it accordingly .....
-(BOOL) isPasswordValid:(NSString *)pwd
{
if ( [pwd length]<4 || [pwd length]>20 ) return NO; // too long or too short
NSRange rang;
rang = [pwd rangeOfCharacterFromSet:[NSCharacterSet letterCharacterSet]];
if ( !rang.length ) return NO; // no letter
rang = [pwd rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet]];
if ( !rang.length ) return NO; // no number;
return YES;
}

Answer 3

I guess the problem is in the alphanumericCharacterSet, here is a part from doc:
Informally, this set is the set of all characters used as basic units
of alphabets, syllabaries, ideographs, and digits.
So, I am expecting it would allow the unwanted characters to you.
You may also try using Regex:
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"^[a-z\\d]+$" options:NSRegularExpressionCaseInsensitive error:&error];
NSUInteger matches = [regex numberOfMatchesInString:str options:NSMatchingReportCompletion range:NSMakeRange(0, [str length])];
BOOL hasMatches = (matches > 0) && !error;

Answer 4

Try this
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
NSCharacterSet *charactersToBlock = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
return ([string rangeOfCharacterFromSet:charactersToBlock].location == NSNotFound);
}

Answer 5

Try this :
NSCharacterSet *blockedCharacters = [[[NSCharacterSet alphanumericCharacterSet] invertedSet] retain];
- (BOOL)textField:(UITextField *)field shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)characters
{
return ([characters rangeOfCharacterFromSet:blockedCharacters].location == NSNotFound);
}