Can someone please help me with using Regex with NSPredicate?

NSString *regex = @"(?:[A-Za-z0-9])";
NSPredicate *pred = [NSPRedicate predicateWithFormat:@"SELF MATCHES %@", regex];
if ([pred evaluateWithObject:mystring])
{
  //do something
}

testing the above wth mystring - qstring123 doesn't seem to work. I am expecting it to enter the if condition because it supposedly should match the regex.

Besides, I need a regex for alpha numberic allowing commas and spaces.

will this work?

@"(?:[A-Za-z0-9])*(?:,[A-sa-z0-9)*(?:\s[A-sa-s0-9])"

Please help.