App State, Application life cycle, View State

App States

1. Not Running

• The app is not in memory. It has either not been launched or was terminated by the system or the user.

2. Inactive

• The app is in the foreground but not receiving user input.
• Typically, this occurs during transitions, such as when a phone call is received or the app is about to become active.

3. Active

• The app is in the foreground and receiving user input.
• This is the state where most app interactions and updates occur.

4. Background

• The app is running in the background and executing code.
• Apps can perform tasks like fetching data, playing music, or completing a download in this state.
• If the app doesn’t have a background task, it transitions quickly to the Suspended state.

5. Suspended

• The app is in memory but not executing any code.
• This state is managed by the system to preserve battery life and system resources.
• If memory pressure occurs, the system may terminate the app.

Lifecycle Callbacks

The app’s state transitions are handled using the AppDelegate or the newer SceneDelegate in multi-scene apps. Key lifecycle methods include: