iOS App Lifecycle: From AppDelegate to SwiftUI — What Every Developer Should Know

Wed, 01 Apr 2026 00:00:00 +0000

There’s a question I ask every iOS candidate I interview: “Walk me through what happens from the moment a user taps your app icon to the moment they’re looking at your home screen.”

Most developers answer this with a list of method names. Senior developers answer it with a mental model. Staff engineers answer it by asking a clarifying question first — “Are we talking UIKit or SwiftUI? What iOS deployment target?” — because the answer genuinely differs, and knowing when it differs is the whole point.

AppDelegate on Vasant Patil

iOS App Lifecycle: From AppDelegate to SwiftUI — What Every Developer Should Know