Convert an array of Int to an array of their respective string representations

gistfile1.swift

private static let digitNames =
[0: "Zero", 1: "One", 2: "Two",   3: "Three", 4: "Four",
    5: "Five", 6: "Six", 7: "Seven", 8: "Eight", 9: "Nine"]


extension Array {
    func translateToDigitalNames()-> [String]? {
        let numbers: [Int] = self.filter { $0 is Int }.map { $0 as Int }
        
        if numbers.count != self.count {
            return nil
        }
        
        return Array.translateToDigitalNames(numbers)
    }
    
    private static func translateToDigitalNames(numbers: [Int])-> [String] {
        return numbers.map { self.translateToDigitalName($0) }
    }
    
    private static func translateToDigitalName(var number: Int) -> String {
        var output = ""
        
        while number > 0 {
            output = digitNames[number % 10]! + output
            number /= 10
        }
        return output
    }
}