Swift+Extensions.swift

extension String {
    ///Get array of individual strings
    func array() -> [String] {
        return self.characters.map({ (char) -> String in
            return String(char).lowercaseString
        })
    }
    
    ///Get `NSCountedSet` from string
    func countedSet() -> NSCountedSet {
        return NSCountedSet(array: self.array())
    }
    
    func isAnagram(string: String) -> Bool {
        guard string.characters.count == self.characters.count else {
            return false
        }
        return self.countedSet().isEqual(string.countedSet())
    }
}

func isAnagram(string1: String, string2: String) -> Bool {
    
    func countedSet(string: String) -> NSCountedSet {
        let array = string.characters.map { (character) -> String in
            return String(character)
        }
        return NSCountedSet(array: array)
    }
    
    return countedSet(string1).isEqual(countedSet(string2))
}

print(isAnagram("abcd", string2: "dbca"))