NSURLRequest objects represent a URL load request in a manner independent of protocol and URL scheme.
NSURLRequest encapsulates two basic data elements of a load request: the URL to load, and the policy to use when consulting the URL content cache made available by the implementation.
NSURLRequest is designed to be extended to support additional protocols by adding categories that provide accessor methods for your own protocol-specific properties. Those methods can get and set the actual values by calling the
The mutable subclass of