Protocols & Extensions basics
Define protocols, make types conform, extend with default implementations, and understand static vs instance requirements.
Protocols & Extensions basics is a free Swift Academy lesson on CoddyKit. This is lesson 1 of 3. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 3 lessons in total.
Intro
Swift protocols define a contract of methods/properties. Types adopt protocols to gain shared behavior. Extensions add functionality or default implementations.
Define protocol
Declare a protocol with required methods or properties.
protocol Greetable {
func greet() -> String
}Conformance
A type conforms by implementing all protocol requirements.
struct Person: Greetable {
var name: String
func greet() -> String {
return "Hi, I am \\(name)"
}
}
print(Person(name:"Ada").greet())Extensions
Use extensions to make existing types conform to a protocol.
extension Int: Greetable {
func greet() -> String { return "Number \\(self)" }
}
print(5.greet())Default implementation
Extensions can add default implementations, so conforming types don't have to implement everything.
extension Greetable {
func greet() -> String { return "Hello!" }
}
struct Dog: Greetable { }
print(Dog().greet())Static vs instance
Protocols can require static and instance members.
protocol Identifiable {
static var typeID: String { get }
var id: Int { get }
}
struct Item: Identifiable {
static var typeID = "Item"
var id: Int
}
print(Item.typeID, Item(id:1).id)Protocol Q
Quick check: What is the main role of a protocol?
Recap
Recap: Define protocols for shared contracts, conform with types, extend existing types, add defaults, and use static vs instance requirements.
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Frequently Asked Questions
Is the “Protocols & Extensions basics” lesson free?
Yes — any 3 lessons of the Swift Academy learning path, including “Protocols & Extensions basics”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 3 lessons in total.
What will I learn in “Protocols & Extensions basics”?
Define protocols, make types conform, extend with default implementations, and understand static vs instance requirements. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Swift Academy?
No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 3.
How long does the “Protocols & Extensions basics” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Swift Academy lesson?
Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Protocols & Extensions basics
- Protocol extensions vs type extensions
- Static vs instance requirements