A Practical Guide to SwiftUI App Structure and Lifecycle Management
- Eric Palma
- May 7
- 4 min read
One of the most important topics in iOS development in general that often seems to come as an afterthought is app lifecycle. App lifecycle refers to the different stages that your iOS app could be in.
Here’s a simple breakdown of the main stages:
Not Running:
The app is completely closed and isn’t using any resources.
Example: You haven’t opened the app yet, or you manually quit it from the app switcher (swipe up on the app).
Inactive:
The app is in the foreground but isn’t receiving user input.
Example: When you get a call or a notification banner while using the app.
Active:
The app is in the foreground and responding to user interactions.
Example: You’re actively scrolling through a social media feed or typing in a search bar.
Background:
The app is no longer visible on the screen but is still running in the background.
Example: You switch to another app, but your app is playing music or downloading a file.
Suspended:
The app is in the background but not actively doing anything. It stays in memory so you can reopen it quickly.
Example: Apps like the calculator or notes might get suspended when you switch away from them.
To get a more concrete idea, imagine this scenario:
You have Instagram installed on your phone.
You restart your phone.
Upon restarting, the Instagram app is Not Running.
You find your Instagram app and open it, now it's Active.
You get a text message so you swipe down on your phone to view your notifications, the app goes to Inactive.
You go back to the app, now it's Active again. Now you begin uploading a post/story, while the app is doing that you switch to another app, now your app is in Background mode. You aren't interacting with it directly, but it's still in the process of uploading your post/story.
Instagram finishes uploading your post, but you are still using a different app, so now the app gets switched to Suspended.
As an iOS developer, understanding your app's lifecycle stages is crucial because it helps you manage your app’s behavior in different scenarios. For instance, when your app moves to the background—like when the user switches to another app—you may need to pause ongoing tasks, such as a video playback or a file download, to save resources and improve battery life. Similarly, when the app becomes active again, you can resume those tasks seamlessly for the user.
Want to learn how SwiftUI apps are structured under the hood, how the lifecycle integrates with SwiftUI’s scene management, and how to handle state transitions gracefully? Unlock the full post to dive into the anatomy of a SwiftUI app and advanced lifecycle techniques.
Want to read more?
Subscribe to curiousalgorithm.com to keep reading this exclusive post.
