What’s the difference between a protocol and a class?
Swift version: 5.0
When writing protocol-oriented Swift, protocols and classes become fairly similar, but they are never the same.
In their basic form, a protocol describes what an unknown type of object can do. You might say it has two or three properties of various types, plus methods. But that protocol never includes anything inside the methods, or provides actual storage for the properties.
In a more advanced form, you can write extensions on your protocols that provide default implementations of the methods. You still can’t provide storage for properties, however.
In comparison, classes are concrete things. While they might adopt protocols – i.e., say they implement the required properties and methods – they aren’t required to do that. You can create objects from classes, whereas protocols are just type definitions. Try to think of protocols as being abstract definitions, whereas classes and structs are real things you can create.
SPONSOR Tired of wasting time debugging your Swift app? Instabug’s SDK is here to help you minimize your debugging time by providing you with complete device details, network logs, and reproduction steps with every bug report. All data is attached automatically. It only takes a line of code to setup. Get started for free.
Available from iOS 8.0
Did this solution work for you? Please pass it on!
Other people are reading…
- How to run code when an object is destroyed
- How to use try/catch in Swift to handle exceptions
- How to group arrays using dictionaries
- How to install a beta version of Swift
- How to toggle a boolean value
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
