监听textFiled单个字符输入 并做筛选

筛选输出为2的倍数的字符

    let textFile = UITextField.init(frame: CGRectMake(0, 100, 400, 50))    textFile.backgroundColor = UIColor.brownColor()    _ = textFile.rx_text        .map{ (temp : String) -> Int in            if let lastStr = temp.characters.last {                if let intTemp = Int(String(lastStr)) {                    return intTemp                }            }            return -1        }        .filter{            $0 % 2 == 0        }        .subscribeNext{            print($0)    }    view.addSubview(textFile)