PasswordGenerator.swift

class PasswordGenerator {
    
    private static let Lowercase = "abcdefghijklmnopqrstuvwxyz".split()
    private static let Uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split()
    private static let Symbols = "!@#$%^&*?".split()
    private static let Numbers = "0123456789".split()
    
    class func generate(length: Int = 10) -> String {
        let allLetters = (Lowercase + Uppercase + Symbols + Numbers).shuffle()
        var password = ""
        var i = 0
        var generator = allLetters.generate()
        while let letter = generator.next() where i < length {
            password += letter
            ++i
        }
        return password
    }
    
}

extension String {
    
    func split(separator: String = "") -> [String] {
        if separator.isEmpty {
            var items = [String]()
            for character in characters {
                items.append(String(character))
            }
            return items
        }
        return componentsSeparatedByString(separator)
    }
    
}

extension Array {
    
    func shuffle() -> [T] {
        var shuffled = self
        for i in 0..<shuffled.count {
            let j = Int(arc4random()) % shuffled.count
            shuffled.insert(shuffled.removeAtIndex(j), atIndex: i)
        }
        return shuffled
    }

}

PasswordGenerator.generate(20)