Protocols in iOS Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a protocol in Swift?

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. Classes, structs, or enums can adopt protocols to provide actual implementations.

beginner

How do you declare a protocol in Swift?

Use the protocol keyword followed by the protocol name and curly braces. Inside, list the required methods or properties without implementations.

intermediate

Can a Swift protocol require properties? If yes, what kind?

Yes, protocols can require properties. They can specify whether the property must be gettable or gettable and settable, but they do not provide storage or implementation.

beginner

What does it mean for a type to conform to a protocol?

It means the type agrees to implement all the requirements defined in the protocol, such as methods and properties, ensuring it meets the protocol's contract.

intermediate

Can protocols be used as types in Swift? Give an example.

Yes, protocols can be used as types to define variables, parameters, or return types. For example, a variable of type MyProtocol can hold any instance of a type that conforms to MyProtocol.

Which keyword is used to define a protocol in Swift?

A class

B protocol

C interface

D struct

Swift uses the keyword protocol to define protocols.

What must a type do to conform to a protocol?

A Implement all required methods and properties

B Inherit from the protocol

C Override the protocol

D Declare the protocol as a variable

Conforming means implementing all the protocol's required methods and properties.

Can a protocol specify property requirements without providing storage?

A No, it must provide storage

B Only for classes

C Yes, it only specifies get/set requirements

D Only for structs

Protocols specify whether properties must be gettable or settable but do not provide storage.

Which of these can adopt a protocol in Swift?

A Class, struct, and enum

B Only classes

C Only structs

D Only enums

Classes, structs, and enums can all adopt protocols.

Can you use a protocol as a type for a variable?

A Only inside functions

B No, protocols are not types

C Only if the protocol is a class

D Yes, to hold any conforming instance

Protocols can be used as types to hold any instance that conforms to them.

Explain what a protocol is in Swift and why it is useful.

Think about how protocols help different types agree on a set of rules.

Describe how a type conforms to a protocol and what happens if it does not implement all requirements.

Consider what the compiler expects when you say a type adopts a protocol.