Protocol declaration syntax in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a protocol in Swift?

A protocol in Swift is like a blueprint that defines methods, properties, or other requirements that a class, struct, or enum can adopt and implement.

beginner

How do you declare a protocol in Swift?

Use the keyword protocol followed by the protocol name and curly braces containing the requirements. For example:<br>

protocol MyProtocol {
    func doSomething()
}

intermediate

Can protocols declare properties in Swift? If yes, how?

Yes, protocols can declare properties. They specify whether the property must be gettable or gettable and settable. For example:<br>

protocol Example {
    var name: String { get set }
    var id: Int { get }
}

beginner

What does it mean when a protocol property is declared with { get } only?

It means the property must be readable (gettable) but does not have to be writable (settable).

intermediate

How do you specify that a protocol inherits from other protocols?

List the protocols separated by commas after the protocol name. For example:<br>

protocol Combined: ProtocolA, ProtocolB {
    // requirements
}

Which keyword is used to declare a protocol in Swift?

A class

B interface

C struct

D protocol

In Swift, the keyword protocol is used to declare a protocol.

How do you declare a read-only property requirement in a protocol?

A var propertyName: Type { get }

B var propertyName: Type

C let propertyName: Type

D var propertyName: Type { get set }

Using { get } means the property must be readable but not necessarily writable.

Can a struct adopt a protocol in Swift?

A Yes, structs can adopt protocols.

B No, only classes can adopt protocols.

C Only enums can adopt protocols.

D Protocols cannot be adopted by any type.

In Swift, classes, structs, and enums can all adopt protocols.

How do you declare a protocol that inherits from two other protocols named A and B?

A protocol NewProtocol inherits A, B

B protocol NewProtocol extends A, B

C protocol NewProtocol: A, B

D protocol NewProtocol implements A, B

Use a colon and list the protocols separated by commas after the protocol name.

Which of the following is NOT a valid protocol requirement?

A var count: Int { get set }

B private func helper()

C init(value: Int)

D func doWork()

Protocol requirements cannot have access modifiers like private.

Explain how to declare a protocol in Swift and include property and method requirements.

Think about the blueprint idea and how you list requirements.

Describe how protocol inheritance works in Swift and why it might be useful.

Consider how you can build on existing blueprints.