View Model

class ViewModel {
    var numberVariable = Variable<String?>(nil)
    var isEvenObservable: Observable<String>!
    
    init () {
        isEvenObservable = numberVariable.asObservable()
            .map {number in
                guard let numberTemp = number else {return "Invalid"}
                guard let numberIsNumber = Int(numberTemp) else {return (numberTemp + " is not number")}
                return (numberIsNumber % 2 == 0) ? numberTemp + " is Even" : numberTemp + " is Odd"
        }
        
    }
    
}