The Tax income simulator

When we are developing an app, we know that some variables of a function shouldn't contain certain values, but are you sure of this? How can we develop and check that everything has its right value?

In this recipe, we will learn how to check that the values are right during the development stage. To simulate this, let's create an app where we are sure that there will be people trying to cheat the values; in this case, let's create an app to calculate tax income.

Getting ready

Create a project called Chapter 7 Tax Income and make sure that you are in debug mode. To do this, click on the project schema and select Edit schema..., as shown in the following screenshot:

Click on the Run option located on the left-hand side, then make sure that the Info tab is selected, and finally, make sure that the build option is on the Debug mode. We will have some explanations later.

Once these steps have been checked, we need to open the project settings and create a macro called DEBUG_MODE...