Change local storage for priced items

I was porting your C# code to F# when I've realized that something didn't add up and most notably how merging quantities is achieved in the current implementation:

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Cart.cs

Lines 92 to 110 in a552bc5

    
           private void Apply(ProductAdded @event) 
        
           { 
        
               Version++; 
        
               var newProductItem = @event.ProductItem; 
        
               var existingProductItem = FindProductItemMatchingWith(newProductItem); 
        
               if (existingProductItem is null) 
        
               { 
        
                   ProductItems.Add(newProductItem); 
        
                   return; 
        
               } 
        
               ProductItems.Replace( 
        
                   existingProductItem, 
        
                   existingProductItem.MergeWith(newProductItem) 
        
               ); 
        
           }

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Products/PricedProductItem.cs

Lines 46 to 52 in a552bc5

    
           public PricedProductItem MergeWith(PricedProductItem pricedProductItem) 
        
           { 
        
               if (!MatchesProductAndPrice(pricedProductItem)) 
        
                   throw new ArgumentException("Product or price does not match."); 
        
               return new PricedProductItem(ProductItem.MergeWith(pricedProductItem.ProductItem), UnitPrice); 
        
           }

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Products/ProductItem.cs

Lines 30 to 36 in a552bc5

    
           public ProductItem MergeWith(ProductItem productItem) 
        
           { 
        
               if (!MatchesProduct(productItem)) 
        
                   throw new ArgumentException("Product does not match."); 
        
               return Create(ProductId, Quantity + productItem.Quantity); 
        
           }

Not only there is a redundant check as part of the current implementation:

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Products/PricedProductItem.cs

Lines 41 to 44 in a552bc5

    
           public bool MatchesProductAndPrice(PricedProductItem pricedProductItem) 
        
           { 
        
               return ProductId == pricedProductItem.ProductId && UnitPrice == pricedProductItem.UnitPrice; 
        
           }

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Products/ProductItem.cs

Lines 46 to 49 in a552bc5

    
           public bool MatchesProduct(ProductItem productItem) 
        
           { 
        
               return ProductId == productItem.ProductId; 
        
           }

but actually considering how data are stored:

samples/CQRS_Flow/.NET/Carts/Carts/Carts/Cart.cs

Line 21 in a552bc5

public IList<PricedProductItem> ProductItems { get; private set; } = default!;

I think it would be relevant to use a map or a dictionary to store the priced items.

It would make the whole consistency check a lot simpler.

Also why bother throwing exceptions when you can add a product when the same product isn't already part of the collection and then merge quantities when it is.

Wdyt?

@natalie-perret-1986, I think that the suggestion makes sense. Would you be willing to send a PR aligning that? 🙂

@natalie-perret-1986, I think that the suggestion makes sense. Would you be willing to send a PR aligning that? 🙂

Sure I will

	private void Apply(ProductAdded @event)
	{
	Version++;

	var newProductItem = @event.ProductItem;

	var existingProductItem = FindProductItemMatchingWith(newProductItem);

	if (existingProductItem is null)
	{
	ProductItems.Add(newProductItem);
	return;
	}

	ProductItems.Replace(
	existingProductItem,
	existingProductItem.MergeWith(newProductItem)
	);
	}

	public PricedProductItem MergeWith(PricedProductItem pricedProductItem)
	{
	if (!MatchesProductAndPrice(pricedProductItem))
	throw new ArgumentException("Product or price does not match.");

	return new PricedProductItem(ProductItem.MergeWith(pricedProductItem.ProductItem), UnitPrice);
	}

	public ProductItem MergeWith(ProductItem productItem)
	{
	if (!MatchesProduct(productItem))
	throw new ArgumentException("Product does not match.");

	return Create(ProductId, Quantity + productItem.Quantity);
	}

	public bool MatchesProductAndPrice(PricedProductItem pricedProductItem)
	{
	return ProductId == pricedProductItem.ProductId && UnitPrice == pricedProductItem.UnitPrice;
	}

	public bool MatchesProduct(ProductItem productItem)
	{
	return ProductId == productItem.ProductId;
	}