Adding computed properties in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a computed property in Swift?

A computed property calculates a value each time it is accessed instead of storing it. It uses a getter and optionally a setter to compute the value dynamically.

beginner

How do you define a read-only computed property in Swift?

You define a computed property with only a getter, like this:<br>

var area: Double {<br>  return width * height<br>}

This property calculates and returns the area without storing it.

intermediate

Can computed properties have setters in Swift? What does that mean?

Yes, computed properties can have setters. This means you can assign a value to the property, and the setter will run code to update other properties or perform actions based on the new value.

beginner

Why use computed properties instead of stored properties?

Computed properties save memory because they don’t store values. They always provide up-to-date values based on other data, making your code cleaner and more flexible.

beginner

Example: How to add a computed property 'fullName' combining 'firstName' and 'lastName'?

You can write:<br>

var fullName: String {<br>  return "\(firstName) \(lastName)"<br>}

This property returns the full name by joining first and last names.

What does a computed property in Swift do?

A Is only used for constants

B Stores a fixed value in memory

C Calculates its value every time it is accessed

D Cannot have a setter

Computed properties calculate their value dynamically each time you access them.

Which keyword is used to define a computed property in Swift?

A var

B let

C func

D class

Computed properties are defined using 'var' because their value can change.

Can a computed property have a setter in Swift?

A Only inside classes

B No, computed properties are read-only

C Only if marked with 'let'

D Yes, to update other properties when assigned

Computed properties can have setters to allow assigning values that update other data.

What happens if you omit the setter in a computed property?

A The property cannot be accessed

B The property becomes read-only

C The property stores a value

D The code will not compile

Without a setter, the computed property is read-only and only has a getter.

Why might you choose a computed property over a stored property?

A To always get up-to-date values without extra storage

B To save the value permanently

C To make the property constant

D To avoid using functions

Computed properties calculate values on demand, so they don’t use extra memory and always reflect current data.

Explain what a computed property is and how it differs from a stored property in Swift.

Think about how the value is provided or stored.

Write a simple example of a computed property that returns the full name by combining first and last names.

Use string interpolation inside the getter.