Replacing text in a string using replacingOccurrences(of:)

Replacing Occurrences of Strings in Swift: A Unicode Trap

String replacement in Swift looks trivial—until you touch emojis, flags, or anything outside the Unicode BMP. Then subtle Unicode details start leaking through the NSString class. Here’s a concrete example that exposes the problem.

1. The Surprising Result

let result = "🇨🇦🇺🇸".replacingOccurrences(of: "🇦🇺", with: "🇳🇮")

Result:

🇨🇳🇮🇸

At first glance…