What is a delegate in iOS?
Swift version: 5.6
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 UITableViewDelegate. 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.
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.
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…
- UIImageWriteToSavedPhotosAlbum(): how to write to the iOS photo album
- How to handle the HTTPS requirements in iOS with App Transport Security
- How to detect your iOS app is running on macOS Catalyst
- How to use compiler directives to detect the iOS Simulator
- How to identify an iOS device uniquely with identifierForVendor
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
