Understanding protocols

Imagine an app used by a fast-food restaurant. The management has decided to show calorie counts for the meals being served. The app currently has the following class, structure, and enumeration, and none of them have calorie counts implemented:

• A Burger class
• A Fries structure
• A Sauce enumeration

Let's see how you can add calorie counts to all three, and later write a function to calculate the total calorie count.

Add the following code to your playground to declare the Burger class, the Fries structure, and the Sauce enumeration:

class Burger {
}
struct Fries {
}
enum Sauce { 
     case chili 
     case tomato
}

These represent the existing class, structure, and enumeration in the app. Don't worry about the empty definitions, as they are not required for this lesson. As you can see, none of them have calorie counts.

You will resolve this issue by using protocols...