Title Case Extension for Swift 4

titlecase.swift

extension String {
	func titlecased() -> String {
		if self.count <= 1 {
			return self.uppercased()
		}
		
		let regex = try! NSRegularExpression(pattern: "(?=\\S)[A-Z]", options: [])
		let range = NSMakeRange(1, self.count - 1)
		var titlecased = regex.stringByReplacingMatches(in: self, range: range, withTemplate: " $0")
		
		for i in titlecased.indices {
			if i == titlecased.startIndex || titlecased[titlecased.index(before: i)] == " " {
				titlecased.replaceSubrange(i...i, with: String(titlecased[i]).uppercased())
			}
		}
		return titlecased
	}
}

Getting a rare crash while using above code

Crashed: com.apple.main-thread
0 libswiftCore.dylib 0x203b00 specialized fatalErrorMessage(:_:file:line🎏) + 296
1 libswiftCore.dylib 0x20910c specialized BidirectionalCollection._distance(from:to:) + 732
2 libswiftCore.dylib 0x21fca0 specialized copyCollectionToContiguousArray(:) + 64
3 libswiftCore.dylib 0x24dbf8 specialized String.uppercased() + 1028
4 appName 0x7dcaa4 String.titlecased() + 65 (StrExtension.swift:65)

Hi @SunnyAstegic, which line do you get the crash from? Also, do you have an idea about the input?