This is the seventh part of the solution for Papa Bob's Mega Challenge. In this part, we're going to create a 'Lookup Table' to store pricing information for the different pizza options.
Step 1: Add a New Table to the Database
Navigate in the Server Explorer to the PapaBobsDbEntities database and expand it to show the folders inside. Right-click on the Tables folder and select Add > New Table:
In the table's design view, rename the table to 'PizzaPrice' and add the following properties:
Next, click 'Update' in the upper left-hand corner to commit the changes:
Right-click on the PizzaPrices table in the Server Explorer and select 'Show Table Data'. Input the following values for the current pizza prices:
Next, navigate to PapaBobsEntities.edmx within the Persistence layer. Right-click on any of the surface area not occupied by the Order model and select 'Update Model from Database...':
From the resulting dialog window, choose to add the PizzaPrices table from the database and confirm your selection:
At this point, a class called PizzaPrice should have been added to your Model next to 'Order':
Now, build your solution to ensure everything was added properly.
Step 2: Creating a PizzaPriceRepository and DTO Class
Because there is now a model for the pizza's prices, we can essentially do the reverse of what we did with the Order. Instead of passing the information to the Persistence, we can pass it from the persistence to the Domain.
To do this, we'll need to start by creating a PizzaPriceRepository class in the Persistence layer:
Then, create a new PizzaPriceDTO class within the DTO class library. Populate its properties with those found in the Entity-generated PizzaPrice class:
Step 3: Converting PizzaPrice to DTO
Returning to PizzaPriceRepository, create a new method that will retrieve the current prices for the pizza. Call this method GetPizzaPrices():
Inside this method, write the following code to retrieve the most recent prices for the pizza:
This First() method will return the first (most recent) entry in the database to the caller, setting the prices variable equal to that latest entry. Create another method beneath GetPizzPrices() to convert the PizzaPrice object to a DTO and return that new object:
Inside this method, we'll do much the same as we did in the OrderRepository when converting to an Entity; only this time converting to a DTO:
Return to the GetPizzaPrices() method, making the following changes and calling the convertToDTO() method:
Step 4: Creating a PizzaPriceManager
Now that we've saved the pizza prices into a Data Transfer Object, we can access it in the Domain layer for use in calculating the cost of the order. Because this is a separate responsibility from managing the order, we'll create a new PizzaPriceManager class. Its first responsibility will be to retrieve the pizza prices from the Persistence layer:
Then, we'll create another public method that will return the calculated pizza cost of a given order back to the caller:
This method will coordinate method calls that determine the cost for individual parts of the pizza, such as Size, Crust and Toppings, then add the returned totals together to determine the total cost. To do this, we'll need to first create a prices variable that holds the pizza prices:
Then, we'll add to the cost variable through the use of three helper methods that each take in the order and prices:
Step 5: Calculating Costs
Generate a method stub for each of the above methods to begin filling in the code logic. We'll start with the first:
Inside, we'll create a switch statement that covers all the cases for the order's Size property:
In each case, the cost variable will be assigned the value of the corresponding size cost from the list of prices:
Now, move to the calculateCrustCost() method and fill in the same swith() statement structure:
Following the same structure, assign the cost as is appropriate for each case:
Finally, we'll move our attention to the calculateToppings() method:
A switch() statement will not apply here, because each topping is its own property within the order. Instead, we can make use of ternary operators to add to the cost, like so:
Repeat this process for all the toppings in this method:
Step 6: Add the Order Price to the Order
Now that the necessary operations to calculate the price have been performed, return to the OrderManager. From here, we'll set the TotalCost property to the returned value of the PizzaPriceManager's CalculateCost() method, passing in the orderDTO:
Now, save your solution and run the project, creating an order and submitting it:
Navigate to the Orders table to see the order placed, along with its calculated total cost:
Conclusion:
This concludes this section of the solution for Papa Bob's Mega Challenge. We've now populated every property of the order, gathered the total cost and saved it to the database. In the next part of the solution, we'll create a system for visually updating the order prices to the user.