Question

To clarify, I want to check for valid characters. For first name, last name I want to check for [A-Za-z]. For Email I want to check for chars valid for email.

What algorithm would I use to CHECK user input? Specifically, I’d like to CHECK the user’s first name, last name and email address for valid characters before I add to database.

Obviously, something like this isn’t sufficient:

    if ( [firstName.text isEqualToString:@''] || [lastName.text isEqualToString:@''] || [emailAddress.text isEqualToString:@'']) { ... } 

Answer 1

Revised for your edit:

What you probably want to look at is NSCharacterSet. It lets you define explicit sets of characters, which you can then use to test strings for presence of those characters. A trivial example:

NSCharacterSet* nonAlphaNumericSet = [[NSCharacterSet alphanumericCharacterSet] invertedSet]; if ([someString rangeOfCharacterFromSet:nonAlphaNumericSet].location != NSNotFound) {     NSLog(@'It's not alphanumeric!'); }