When to use Classes over Protocols and Structs over Enums?

Let's first talk about Class vs. Protocol

A class and protocol are very similar, but a protocol defines the necessary components something must have, and the class simply say what is included. There is an example that you can see in the Swift Protocols course. You can have a class called plane, and a subclass of jet plane. You can inherit all the properties from airplane to jet plane and add on more. However, if you have a class called bird, it will be kind of awkward. A bird is not a type of airplane and an airplane is not a type of bird, in this loose relationship, you would use a protocol. The protocol can be something like Flyable, and it defines all the necessary components for flying. The class can inherit from that protocol, and things will make sense. I am not sure if I have the best explanation here, but be sure to check out this course for more info and explanations. https://teamtreehouse.com/library/swift-20-protocols If you want to learn more about protocols, you can check the Apple documentary. https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html

As for struct and enum, it is a lot simpler to explain. An enum is like a multiple choice. You choose the value instead of creating a value, even though you can pass in values in enum also, but think of it as a multiple choice. Struct is similar to class, you create the values and modify things and treat it like an object.

Hope that helps you :)