RNCachingURLProtocol is a simple shim for the HTTP protocol (that’s not nearly as scary as it sounds). Anytime a URL is downloaded, the response is cached to disk. Anytime a URL is requested, if we’re online then things proceed normally. If we’re offline, then we retrieve the cached version.
The point of RNCachingURLProtocol is mostly to demonstrate how this is done. The current implementation is extremely simple. In particular, it doesn’t worry about cleaning up the cache. The assumption is that you’re caching just a few simple things, like your “Latest News” page (which was the problem I was solving). It caches all HTTP traffic, so without some modifications, it’s not appropriate for an app that has a lot of HTTP connections (see MKNetworkKit for that). But if you need to cache some URLs and not others, that is easy to implement.
You should also look at AFCache for a more powerful caching engine that is currently integrating the ideas of RNCachingURLProtocol.
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To build, you will need the Reachability code from Apple (included). That requires that you link with
SystemConfiguration.framework. -
At some point early in the program (usually
application:didFinishLaunchingWithOptions:), call the following:[NSURLProtocol registerClass:[RNCachingURLProtocol class]]; -
There is no step 3.
For more details see Drop-in offline caching for UIWebView (and NSURLProtocol).
See the CachedWebView project for example usage.
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