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I need to create a simple payments validator. On the following class diagram, I tried to present the model of payments. As you can see, each payment type inherits from Payments class.

Payments diagram

Now I want to work with these payments but hide the details so the user can only access what he needs. And those things are are:

Load payments from path and return list of payments

Save payments to path

Update input payments list and return updated list

I am not sure if the way I am doing it is correct.

My idea would be to use Facade design pattern, so PaymentsModel class which would contain following methods should be created:

public class PaymentsModel
{

    IList<ToBePaidPaymentsDto>  GetToBePaidPayments(string path){
         return new IList<ToBePaidPaymentsDto>();
    }

    IList<DonePaymentsDto>  GetDonePayments(string path){
         return new IList<DonePaymentsDto>();
    }

    IList<MissedPaymentsDto>  GetMissedPayments(string path){
         return new IList<MissedPaymentsDto>();
    }

    ...

}

Then create abstract class:

public abstract class Payments<T> 
{
    protected string Delimiter {get; private set;}
    protected int NumberOfHeaders {get; private set;}

    public abstract IList<T> LoadRecords(string path);

    public abstract IList<T> UpdateRecords(IList<T> records);

    public void SaveRecords(string path, DataGridViewRowCollection records)
    {
    }

}

where T is Data Transfer Object depending on the type of payments, so:

ToBePaidPayments class would use ToBePaidPaymentsDto

DonePayments class would use DonePaymentsDto

as presented below

public class PaymentsToBePaid : Payments<IcsToBePaidPaymentDto> {

    public override IList<IcsToBePaidPaymentDto> LoadRecords(string path){

        return null;
    }


    public override  IList<IcsToBePaidPaymentDto> UpdateRecords(IList<IcsToBePaidPaymentDto> records){

        return null;
    }

}

and

public class PaymentsDone : Payments<IcsDonePaymentDto>
{
    public override IList<IcsDonePaymentDto> LoadRecords(string path){

        return null;
    }

    public override IList<IcsDonePaymentDto> UpdateRecords(IList<IcsDonePaymentDto> records){

        return null;
    }

}

Now, my final question is - am I doing this correctly? Am I applying correct design pattern and am I applying it correctly? Thank you for advice.

  • 1
    First off the bat, why do you have 3 objects when a "PaymentStatus" enumeration might suffice? Or do you indeed need 3 separate "queues"? – Moo-Juice Jul 16 '14 at 14:12
  • @Moo-Juice I decided to use different classes because the way reading from file is done - each type of payment is composed of different set of columns from csv which usualy do not overlap. – Macin Jul 16 '14 at 14:15
1

Given your comment that payments have different fields based on their status (and I will therefore assume this is an issue because of database tables), then What I'd do is implement a CsvReader class that has a generic-type argument, that maps Csv fields to the POCO in question. Therefore you'd write a single Csv Importer, and that can then be used to import data regardless of what class you throw at it.

Similarly, you can write a CsvExporter class that does the same thing. Write once, use everywhere.

Some comments:

  1. Remove the Dto extension. We know what a payment is, it can potentially be used in many places (the database, the Csv File, business logic). Dto is relevant in a single, specific scenario.

  2. Consider changing Todo to Pending.

  • Thanks for comments, but I do not really understand the first part of your answer. If I got it correctly, you are suggesting to move reading of file to a distinct class, but it is still unclrear for me how to work with parsed data further on when I have to do some updates on the each type of payments... – Macin Jul 16 '14 at 14:35
  • @Macin, the idea is that your Reader/Writer classes are generic, they are not tied to any particular class. Given a generic-type-parameter, they can read or write any class. So you'd read them in, perform whatever operations you want to - on first class POCOS, and then write them back again (if that is your intent). – Moo-Juice Jul 16 '14 at 14:38
  • May I ask you to write some pseudo code? Maybe your idea is much better than what I did but I just can't imagine it easily enough – Macin Jul 16 '14 at 14:47

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