URLProtocol and Unit Testing An NSURLProtocol object handles the loading of protocol-specific URL data. The NSURLProtocol class itself is an abstract class that provides the infrastructure for processing URLs with a specific URL scheme. You create subclasses for any custom protocols or URL schemes that your app supports. The main point is: All you have to do is define your protocol class and call the registerClass(_:) class method during your app’s launch time so that the system is aware of your protocol.
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