Extension syntax in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an extension in Swift?

An extension in Swift adds new functionality to an existing class, struct, enum, or protocol without modifying the original source code.

beginner

How do you declare an extension for a struct named Person?

Use the syntax: <br>

extension Person {<br>    // new methods or properties<br>}

intermediate

Can extensions add stored properties to types in Swift?

No, extensions cannot add stored properties. They can only add computed properties, methods, initializers, and conform to protocols.

beginner

What is the benefit of using extensions in Swift?

Extensions help organize code better, add functionality to types you don’t own, and conform to protocols without subclassing.

beginner

Show an example of adding a method greet() to a struct Person using extension.

extension Person {<br>    func greet() {<br>        print("Hello!")<br>    }<br>}

Which of the following can you NOT add using a Swift extension?

A Computed properties

B Methods

C Stored properties

D Initializers

Extensions cannot add stored properties, only computed properties, methods, and initializers.

How do you start an extension declaration for a class named Car?

A extension Car { }

B class Car extension { }

C extend Car { }

D Car extension { }

The correct syntax is extension Car { }.

Can extensions in Swift add protocol conformance to existing types?

A No

B Yes

C Only for classes

D Only for structs

Extensions can add protocol conformance to any type.

Which keyword is used to declare an extension in Swift?

A modify

B extend

C add

D extension

The keyword extension is used to declare extensions.

What can extensions NOT do?

A Override existing methods

B Add computed properties

C Add new methods

D Add initializers

Extensions cannot override existing methods.

Explain what Swift extensions are and why they are useful.

Think about how you can add features to existing types without changing their original code.

Describe the syntax of declaring an extension and what you can add inside it.

Remember the basic structure and what features extensions support.