To begin, let's first have a look at the following iOS application lifecycle flowchart:
The application lifecycle includes all of the activity in an app from the time it is deployed until the time it has been removed from a device. Each platform describes the lifecycle in varying terms. In the case of an iOS device, the lifecycle is a collection of application states and methods that must be observed while transitioning between those states. Using the previous image as a reference, iOS apps will always exist in one of the following five states:
Not running: This means your app has either not been launched, or it has been terminated by the system for some reason. If your app is currently not running, it can be transitioned into the inactive state when it's launched.
Inactive: This occurs while the app is in the foreground but does not receive event updates. It also occurs when the device screen automatically turns off to conserve power. This state is usually short...