Flowsy.Db.Repository.Abstractions 0.1.0

Flowsy Db Abstractions

Repository

The interface IRepository represents a mechanism to encapsulate the logic for accessing data in the form of entities, independently of the underlying data store.

Unit Of Work

The interface IUnitOfWork represents an atomic operation for the underlying data store. For a SQL database, a class implementing IUnitOfWork could be a wrapper for IRepository instances sharing a single IDbTransaction object.

For example, to create an invoice, we may need to create two kinds of entities:

• Invoice
  • InvoiceId
  • CustomerId
  • CreateDate
  • Total
  • Taxes
  • GrandTotal
• InvoiceItem
  • InvoiceItemId
  • InvoiceId
  • ProductId
  • Quantity
  • Amount

The way of completing such operation from an application-level command handler could be:

public class IInvoiceRepository : IRepository
{
    Task CreateInvoiceAsync(Invoice invoice, CancellationToken cancellationToken);
}

public class IInvoiceItemRepository : IRepository
{
    Task CreateInvoiceItemAsync(InvoiceItem invoiceItem, CancellationToken cancellationToken);
}

public interface ISalesUnitOfWork : IUnitOfWork
{
    IInvoiceRepository InvoiceRepository { get; }
    IInvoiceItemRepository InvoiceItemRepository { get; }
}

public class CreateInvoiceCommandHandler
{
    private readonly ISalesUnitOfWork _unitOfWork;
    
    public CreateInvoiceCommandHandler(ISalesUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWorkFactory;
    }
    
    public async Task<CreateInvoiceCommandResult> HandleAsync(CreateInvoiceCommand command, CancellationToken cancellationToken)
    {
        // Validate command
        
        var invoice = new Invoice();
        // Populate invoice object from properties of command object
        
        // Begin operation
        // IUnitOfWork inherits from IDisposable and IAsyncDisposable, if any exception is thrown, the current operation shall be rolled back
        _unitOfWork.BeginWork();
        
        // Create the Invoice entity
        var invoiceId = await _unitOfWork.InvoiceRepository.CreateInvoiceAsync(invoice, cancellationToken);
        
        // Create all the InvoiceItem entities
        foreach (var item in command.Items)
        {
            var invoiceItem = new InvoiceItem();
            // Populate invoiceItem object from properties of item object
            
            // Create each InvoiceItem entity
            await _unitOfWork.InvoiceItemRepository.CreateInvoiceItemAsync(invoiceItem, cancellationToken); 
        }

        // Commit the current operation        
        await _unitOfWork.SaveWorkAsync(cancellationToken);
        
        // Return the result of the operation
        return new CreateInvoiceCommandResult
        {
            InvoiceId = invoiceId
        };
    }
}

Note: This document ommits implementation details of IRepository and IUnitOfWork interfaces, focusing on showing how they can be used to encapsulate the logic for creating multiple entities in a single atomic operation.

The Flowsy.Db.Repository.Sql package offers an implementation of IRepository and IUnitOfWork interfaces for SQL databases.