BLACK FRIDAY SALE: Save 50% on all my Swift books and bundles! >>

How to run code when an object is destroyed

Swift version: 5.6

Paul Hudson    @twostraws   

All structs and classes can have initializers, which are special methods that run when those types are created. However, classes can also have deinitializers – code that gets run when an instance of the class is destroyed. This isn’t possible with structs because they only ever have one owner.

Deinitializers never take any parameters, so they are written just as deinit. For example, we could create a simple Person class with an initializer and a deinitializer:

class Person {
    init() {
        print("I'm alive!")

    deinit {
        print("I'm dying!")

If you want to try that in a playground, run this code:

do {
    let person = Person()

Putting the Person instance inside a do block ensures it will be destroyed before the playground finishes, so you should see “I’m alive!” and “I’m dying!”

Deinitializers are extremely important when handling memory that isn’t managed by Swift. For example, if you’re using an external C library and it has allocated RAM, you should free that RAM inside your deinitializer.

Save 50% in my Black Friday sale.

SAVE 50% To celebrate Black Friday, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.

Save 50% on all our books and bundles!

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS 8.0 – learn more in my book Pro Swift

Similar solutions…

About the Swift Knowledge Base

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

Buy Pro Swift Buy Pro SwiftUI Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let us know!

Unknown user

You are not logged in

Log in or create account

Link copied to your pasteboard.