Check if NSString is only letters

Question

What's the best way to make sure an NSString contains only the letters a-z and A-Z.

I've tried the following code but it's not working for some reason:

NSString *myegex = @"[A-Za-z]";
NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", myregex];
if (![emailTest evaluateWithObject:self.initials.text])  {
     // print error
     return;
}

Answer 1

You can do it in a simpler way by creating your own NSCharacterSet then checking the string against that set with rangeOfCharacterFromSet:

//Create character set
NSCharacterSet *validChars = [NSCharacterSet characterSetWithCharactersInString:@"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"];

//Invert the set
validChars = [validChars invertedSet];

//Check against that
NSRange  range = [myString rangeOfCharacterFromSet:validChars];
if (NSNotFound != range.location) {

 //invalid chars found

}

Answer 2

I'm not sure how Objective-C regex engine works, but you can leverage anchors ^ and $ to check if your string starts and finishes with letters by using this regex:

^[A-Za-z]+$

Using your code, would be:

NSString *myegex = @"^[A-Za-z]+$";
NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", myregex];
if (![emailTest evaluateWithObject:self.initials.text])  {
     // print error
     return;
}