validation.swift

struct ChangePasswordViewModel : ViewModel {
    
    var brokenRules: [BrokenRule] = [BrokenRule]() 
    
    var newPassword = Dynamic<String>("")
    var confirmPassword = Dynamic<String>("")
    
    var isValid :Bool {
        mutating get {
            self.brokenRules = [BrokenRule]()
            self.validate()
            return self.brokenRules.count == 0 ? true : false
        }
    }
}

extension ChangePasswordViewModel {
    
    mutating private func validate() {
        
        if newPassword.value != confirmPassword.value {
            self.brokenRules.append(BrokenRule(propertyName: "confirmPassword", message: "Passwords are not matching"))
        }
        
        if (newPassword.value?.count)! < 8 {
            self.brokenRules.append(BrokenRule(propertyName: "newPassword", message: "Password should be at least 8 characters long"))
        }
        
    }
    
}