iOS App Lifecycle

1. Introduction

The iOS app lifecycle refers to the various states an app can be in during its existence on an iOS device. Understanding this lifecycle is crucial for managing app behavior and performance efficiently.

2. Lifecycle States

Key States

Not Running: The app is not launched.
Inactive: The app is running but not receiving events (e.g., during an incoming call).
Active: The app is running in the foreground and receiving events.
Background: The app is in the background but executing code.
Suspended: The app is in the background and not executing code.

3. State Transitions

State Transition Flowchart


                graph TD;
                    A[Not Running] -->|Launch| B[Inactive];
                    B -->|Become Active| C[Active];
                    C -->|Move to Background| D[Background];
                    D -->|Suspend| E[Suspended];
                    E -->|Return to Foreground| C;
                    D -->|Terminate| A;
                    C -->|Inactive| B;

4. Best Practices

Manage App State Effectively

Use applicationDidEnterBackground to save data when entering background state.
Handle memory warnings in applicationDidReceiveMemoryWarning.
Always restore the app's state when transitioning from background to active.

5. FAQ

What happens in the background state?

In the background state, your app can continue executing code for a limited time. It can also perform tasks such as downloading content or fetching data.

What is the difference between suspended and inactive states?

Inactive means the app is running but not receiving events, while suspended means the app is in the background and not executing code at all.