The first tool we will look at is protocols. A protocol is essentially a contract that a type can sign, specifying that it will provide a certain interface to other components. This relationship is significantly looser than the relationship a subclass has with its superclass. A protocol does not provide any implementation to the types that implement them. Instead, a type can implement them in any way that they like.
Let's take a look at how we define a protocol, in order to understand them better.
Let's say we have some code that needs to interact with a collection of strings. We don't actually care what order they are stored in and we only need to be able to add and enumerate elements inside the container. One option would be to simply use an array, but an array does way more than we need it to. What if we decide later that we would rather write and read the elements from the file system? Furthermore, what if we want to write a container that would intelligently...