The Core iOS Developer’s Cookbook, Fifth Edition

Recipe: Detecting Text Patterns

Recipe 6-9 introduces ways to limit users to entering legal characters. From there, it’s just a short hop to matching user input against a variety of legal patterns. Consider a floating-point number. It might be described as an optional sign followed by a whole component followed by an optional decimal and then a fractional component. Or maybe the whole component should be optional but the sign mandatory.

Unfortunately, there are many standard ways of describing things, and those ways increase exponentially when you expand from simple numbers to phone numbers, e-mail addresses, and URLs. Apple has taken care of many of these for you, with its built-in data detector classes, but it often helps to know how to roll ...