Verify that NSString contains only alphanumeric + underscores

Question

I have a string that should only be az, 0-9 and _

How to check the correct input? I tried this, but it accepts a letter like å, ä, ö, ø etc.

NSString *string = [NSString stringWithString:nameField.text]; NSCharacterSet *alphaSet = [NSCharacterSet alphanumericCharacterSet]; [string stringByTrimmingCharactersInSet:alphaSet]; [string stringByReplacingOccurrencesOfString:@"_" withString:@""]; BOOL valid = [[string stringByTrimmingCharactersInSet:alphaSet] isEqualToString:@""]; 

Answer 1

You can create your own character set:

 NSCharacterSet *s = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_"]; 

After that, you flip it to anything that is not in the original line:

 s = [s invertedSet]; 

And then you can use the string method to find out if your string contains anything in the inverted set:

 NSRange r = [string rangeOfCharacterFromSet:s]; if (r.location != NSNotFound) { NSLog(@"the string contains illegal characters"); } 

Answer 2

You can use the predicate:

 NSString *myRegex = @"[A-Z0-9a-z_]*"; NSPredicate *myTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", myRegex]; NSString *string = nameField.text; BOOL valid = [myTest evaluateWithObject:string]; 

Edit: I did not notice that you are using [NSString stringWithString:nameField.text] .

Use nameField.text instead.

Answer 3

A slightly simpler way

 NSMutableCharacterSet *allowedSet = [NSMutableCharacterSet characterSetWithCharactersInString:@"_"]; [allowedSet formUnionWithCharacterSet:[NSCharacterSet alphanumericCharacterSet]]; NSCharacterSet *forbiddenSet = [allowedSet invertedSet]; 

It will combine alphanumeric characters with _underscore.

you can use it for example

 NSRange r = [string rangeOfCharacterFromSet:forbiddenSet]; if (r.location != NSNotFound) { NSLog(@"the string contains illegal characters"); } 

PS. example copied from @DaveDeLong example :)

Answer 4

Create your own character set using [NSCharacterSet characterSetWithCharactersInString:] , then trim as you did to see if the returned string has a length value.

Or you can use invertedSet to remove all unspecified characters if this helps create a cleared string.

Answer 5

You can scroll through each character in a line and check that it is alphanumeric:

 BOOL isMatch = YES; for (int i = 0; i < [string length]; i++) { unichar c = [string characterAtIndex:i]; if (!isalnum(c) && c != '_') { isMatch = NO; break; } } if (isMatch) { // valid } else { // invalid } 

Answer 6

Here you can do it in Swift (as an extension of the String class):

 extension String { func containsValidCharacters() -> Bool { var charSet = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_") charSet = charSet.invertedSet let range = (self as NSString).rangeOfCharacterFromSet(charSet) if range.location != NSNotFound { return false } return true } } 

Answer 7

This is a quick helper if he helps.

 -(BOOL)isString:(NSString *)s{ char letter = 'A'; //BOOL isLetter=NO; for (int i=0; i<26; i++) { NSString *temp = [NSString stringWithFormat:@"%c",letter+i]; if ([s isEqualToString:temp]) { return YES; } } return NO; }