Understanding extensions

Extensions allow you to provide extra capabilities to an object without modifying the object definition. You can use them on Apple-provided objects (where you don't have access to the object definition) or when you wish to segregate your code for readability and ease of maintenance. Here's what an extension looks like:

class ExistingType {
     property1
     method1()
}
extension ExistingType : ProtocolName {
     property2
     method2()
}

Here, this extension is used to provide an additional property and method to an existing class.

Important information

For more information on extensions, visit https://docs.swift.org/swift-book/LanguageGuide/Extensions.html.

Let's look at how to use extensions. You'll start by making the Sauce enumeration conform to the CalorieCountProtocol protocol using an extension in the next section...