Apple's URL loading system is a framework of classes available to interact with URLs. Using these classes together lets us communicate with services that use standard Internet protocols. The classes that we will be using in this chapter to connect to and retrieve information from REST services are as follows:
NSURLSession: This is the main session object. It was written as a replacement for the older
NSURLSessionConfiguration: This is used to configure the behavior of the
NSURLSessionTask: This is a base class to handle the data being retrieved from the URL. Apple provides three concrete subclasses of the
NSURL: This is an object that represents ...