How to log a warning that shows up as a runtime issue in Xcode?

Question

Xcode 8 or 9 started displaying runtime issues. You see a purple icon at the top of the window, and a list in Issue Navigator, next to buildtime issues like compilation warn

Answer 1

CocoaLumberjack framework can be used to capture Run times console logs as well as App's Background wakeup logs.

https://github.com/CocoaLumberjack/CocoaLumberjack

https://github.com/phonegap/phonegap-plugin-push/issues/1988

This way you can capture purple warnings displayed in Xcode9 like below in a file that is maintained inside App Container:-

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Main Thread Checker: UI API called on a background thread: -[UIApplication registerUserNotificationSettings:] PID: 2897, TID: 1262426, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 21