Now that we have our preference service in place, we can now add a functionality to our portfolio window, knowing that the changes done by our user won't be lost.
Probably the most important feature in our application is the ability to add new stocks. Let's start with this one. We will add a click event handler on the btnAddStock button. Inside this handler, we will create a new Stock object using the symbol (in upper case), and quantity entered by the user. Once our stock object is created, we will add it to the table view underneath using the addCustomRow function. We will create this function in just a moment, but for now, remember that it takes two parameters, the table view in which to add the new row and the stock object containing the information we will need to display. Finally, we reset the txtSymbol and txtQuantity text field values so that the user can add a new stock if desired:
btnAddStock.addEventListener(...