Extension for checking if a String is capitalized in Swift 3.0+.

String+Capitalized.swift

extension String {
    func isCapitalized() -> Bool {
        guard self.characters.count > 0 else {
            return false
        }
        return (CharacterSet.uppercaseLetters as NSCharacterSet).characterIsMember(String(self.characters.first!).utf16[String.UTF16Index(0)]);
    }
}

// Test
let token = "Hello World"
let isCapitalized = token.isCapitalized()
print("\"\(token)\" is Capitalized? \(isCapitalized)") // "Hello World" is Capitalized? true