Specifies the caching behavior of the request
NSURLRequest has a cachePolicy property, which specifies the caching behavior of the request according to these constants:
NSURLRequestUseProtocolCachePolicy;NSURLRequestReloadIgnoringLocalCacheData;NSURLRequestReloadIgnoringLocalAndRemoteCacheData;NSURLRequestReturnCacheDataElseLoadNSURLRequestReturnCacheDataDontLoad;NSURLRequestReloadRevalidatingCacheData.
Sources