Sending Requests to a Web Service Using Background App Refresh and Retry Mechanisms for Robust Processing in iOS Apps.

Understanding the Relationship between Interface and Class Definitions in Objective-C: A Guide to Forward-Declaring Classes with @class

Understanding How to Present View Controllers Outside of the Window Hierarchy in iOS Development

Bi-Directional Communication between ViewController and AppDelegate with Swift 2 for iOS: A Comprehensive Guide to Notifications