First, let's define a class called Building that we can inherit from later:

class Building {
    let squareFootage: Int

    init(squareFootage: Int) {
        self.squareFootage = squareFootage
    }
}
var aBuilding = Building(squareFootage: 1000)

Predictably, a class is defined using the class keyword instead of struct. Otherwise, a class looks extremely similar to a structure. However, we can also see one difference here. With a structure, the initializer we created earlier would not be necessary because it would be created for us. With classes, initializers are not automatically created unless all the properties have default values.

Now let's look at how to inherit from this building class:

class House: Building {
...