What’s MetricKit?

MetricKit in a new framework, introduced in iOS 13 (WWDC2019), with which it is intended to gather information (metrics) about battery behavior and application performance. For a registered application, reports on the behavior of said application will be received once a day as a general rule.

Battery

Battery metrics include, among other parameters:

• The state of the mobile network.
• The transfers through the internet.
• The use of the CPU.
• The use of the GPU.
• The energy used to display the application on the screen.
• The use of device location functions.

Performance

From the point of view of performance, metrics are obtained, for example, on:

• The time it takes for the application to open (launch time).
• The response of the application with user interaction.
• The amount of time the application is active.
• The use of memory and disk.

Use

In order to receive metric reports, we need to add a subscription to MXMetricManager (for example in the AppDelegate class):

class AppDelegate: UIResponder, UIApplicationDelegate, MXMetricManagerSubscriber {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        let shared = MXMetricManager.shared
        shared.add(self)

        return true
    }

    func applicationWillTerminate(_ application: UIApplication) {
        MXMetricManager.shared.remove(self)
    }

    // Receive daily metrics
    func didReceive(_ payloads: [MXMetricPayload]) {
       // Process metrics
    }
}

The didReceive method receives an array that contains the information of the last 24 hours (and of all that information that could not be received previously).