单例

num.playground

class NumbersParser: NumberParser {
    static let sharedInstance = NumbersParser()
    func numberToChinese(number: Int) -> String {
        let numbers = String(number).characters
        var finalString = ""
        for singleNumber in numbers {
            let string = singleNumberToChinese(number: singleNumber)
            finalString = "\(finalString)\(string)"
        }
        return finalString
    }
}

let numbersString = NumbersParser.sharedInstance.numberToChinese(number: 2015)

print(numbersString)