System Health

This app monitors the main metrics of your iOS device (CPU, RAM, Battery).

Requirements

Monitor CPU, RAM and Battery and display their current state.
Allows user to define thresholds in the settings. A notification will be posted if the metric goes over this threshold. User can also be notified when it comes back below this threshold.
Monitoring and notifications should also occur if the app is in background.

Context is the object that holds the different monitors and stores. It is passed between view controllers through their initializers.
Alert objects are stored in Core Data, which allows a fast fetch of the most recent alerts to display in DashboardVC

Improvements can be done in Context to factorize and simplify the observation pattern. NotificationCenter implémentation was interesting at first because I needed to observe the status in multiple places but with the current implementation a Delegate pattern would probably be better.
Monitor objects holds an history of all tracked values. While this is barely used for now, it could be used to draw a graph of the CPU/RAM/Battery usage over time.
SettingsStore uses UserDefaults which is fine but it is based on "cpu" or "ram" variables, which is should be improved with an enum.
Background monitoring doesn’t seem to work very efficiently. There is a new BackgroundTask framework in iOS 13 that may be useful but I did not try it yet.
The app use a basic MVC pattern (except the DashboardHeaderView which uses a View Model). If this app was meant to be larger, I would have used an MVVM architecture.