CFStringTransform

NSString is the crown jewel of Foundation. In an age where other languages still struggle to handle Unicode correctly, NSString is especially impressive. Not content to just work with whatever is thrown at it, NSString can parse strings into linguistic tags, determine the dominant language of the content, and convert between every string encoding imaginable. It’s unfairly good.

But as powerful as NSString / NSMutableString are, one would be remiss not to mention their toll-free bridged cousin, CFMutableString—or more specifically, CFStringTransform.

→ nshipster.com/cfstringtransform/

NSString and its toll-free bridged counterpart CFMutableString in Foundation and Core Foundation are highlighted for their exceptional Unicode handling, with CFStringTransform enabling powerful string transformations like stripping diacritics, naming Unicode characters, and transliterating between scripts such as Latin, Cyrillic, and Hiragana.

The function takes a CFMutableStringRef, a range, an ICU transform (e.g., kCFStringTransformStripCombiningMarks or custom ICU strings), and a reverse flag, allowing tasks like normalising user input for search indexing across languages.

For example, transforming multilingual greetings into a Latin, diacritic-free, lowercase form for consistent indexing is achieved in steps or a single ICU transform ("Any-Latin; Latin-ASCII; Any-Lower").

This functionality, unique to Core Foundation, showcases Swift’s interoperability with C-based APIs and its capability to handle complex linguistic tasks, making it invaluable for developers processing diverse text inputs.