NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! >>

What is a delegate in iOS?

Swift version: 5.2

Paul Hudson    @twostraws   

Delegates are extremely common in iOS development, but fortunately they are easy to understand: a delegate is any object that should be notified when something interesting has happened. What that "something interesting" means depends on the context: for example, a table view's delegate gets notified when the user taps on a row, whereas a navigation controller's delegate gets notified when the user moves between view controllers.

When you agree to be the delegate for an object, you will almost certainly need to conform to a specific protocol, such as UITableViewDelete. These protocols will usually have some optional methods that you can implement if you care when something happens, for example, table views can notify you when users deselect a row, but most developers don't care. These protocols may also have some required methods that you must implement.

Hacking with Swift is sponsored by Fernando Olivares

SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.

Try the book!

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

Available from iOS 2.0 – see Hacking with Swift tutorial 1

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 OUR BOOKS
Buy Pro Swift 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 (Vapor Edition) 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 Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 2.8/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.