Like structs, classes are used to model related data under a common type. You will use classes in MonsterTown to model various types of monsters that will be terrorizing your town. Classes differ from structs in a few very important ways, and this section will highlight those differences.
Now that you have a struct representing a town, it is time to make things a little more interesting. Your town is, unfortunately, infested with monsters. This is not good for property values.
Create a new Swift file called Monster. As before, click File → New → File... or press Command-N. Select the Swift File template from the Source section under macOS.
This file will contain the definition for a Monster class ...