FREE: Watch my new YouTube videos, Xcode in 20 Seconds! >>

How to measure a string for Objective-C code

Paul Hudson       @twostraws

Regular Swift code can treat strings like other kinds of sequence, so you can use its count property to read the number of characters it contains:

let str = "Hello, world"
let count = str.count

However, this falls down when you need to work with Objective-C code, for example NSRegularExpression, NSDataDetector, UITextChecker, and more – they use UTF-16 rather than Swift’s extended grapheme clusters, and so if you use count with them you’re likely to miss characters.

Instead, the correct solution is to measure your string’s length using utf16.count, like this:

let input = "This is a test with the URL https://www.hackingwithswift.com to be detected."
let detector = try! NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
let matches = detector.matches(in: input, options: [], range: NSRange(location: 0, length: input.utf16.count))

That guarantees your string’s length is reported fully when interacting with Objective-C code.

Sponsored You’re already busy updating your app for Swift 4.2 and iOS 12, so why not let Instabug help you find and fix bugs? Add just two lines of code to your project and receive comprehensive reports with all the feedback you need to ship a world-class app – click here to learn more!

Available from iOS 7.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Need to know Objective-C fast?

I wrote a book dedicated to teaching Objective-C to developers who already know Swift – it's the fastest way to get up to speed!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Click here to visit the Hacking with Swift store >>