How iOS programs start

First talk about what is UIApplication? Each application has its own UIApplication object and is a singleton, and the first object created after the program starts is the UIApplication object. When the app receives interference, it generates some system events, and UIApplication notifies its proxy object uiapplicationdelegate to handle these events:

1. Application Lifecycle Events (program startup closed to front desk, etc.)

2. System events such as incoming calls

3. Memory Warning

Note: The Uiapplicationmain function is executed until the program exits.

How iOS programs start