BLACK FRIDAY: Save 50% on my Swift books and videos! >>

What does the AppDelegate class do?

Paul Hudson       @twostraws

If you create your app using one of Xcode’s built-in templates, you’ll automatically get an AppDelegate class in AppDelegate.swift, which comes with a handful of empty methods.

This class is supposed to be there to handle application lifecycle events - i.e., responding to the app being launched, backgrounded, foregrounded, receiving data, and so on. However, in practice AppDelegate is often abused as an easy dumping group for shared data – any thing that is used in several view controllers often gets thrown into the app delegate, but that’s nearly always the wrong place for it.

You may also sometimes see folks creating their initial user interface inside AppDelegate. This is broadly a bad idea unless you’re just starting out – if you’ve done this, consider splitting off that layout code either into a coordinator or into a view containment subclass.

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.

Upgrade your apps!

Take on Core ML, ARKit, PDFKit, Core NFC, and more all in one book that's packed with practical projects!

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: 1.0/5

Click here to visit the Hacking with Swift store >>