NEW! Check out my latest book, Testing Swift! >>

What is a computed property?

Paul Hudson       @twostraws

Swift offers us two kinds of property: a stored property is one that saves a value for use later, and a computed property is one that runs some code in order to calculate the value.

As comparison, here’s a Person struct with four stored properties and one computed one. The computed property returns a string based on joining the four stored properties into a sentence.

struct Person {
    var name = "Taylor"
    var favoriteColor = "red"
    var favoriteCity = "Tokyo"
    var favoriteFood = "tea"

    var greeting: String {
        return "Hello, my name is \(name), and I like \(favoriteFood), \(favoriteCity), and the color \(favoriteColor)."
    }
}

Note: Unlike stored properties, Swift requires you to use an explicit type with your computed properties.

Available from iOS 8.0

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Get six books for only $150

The Swift Power Pack includes my first six books for one low price, helping you jumpstart a new career in iOS development – check it out!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Average rating: 4.0/5

Click here to visit the Hacking with Swift store >>