Can I force NSURLConnection to load from cache?

问题:

I had considered writing a custom url cache, but it seems that NSURLCache is supposed to support a disk cache. I'd like to have my iphone app use cached responses without hitting the server at all until the resource becomes stale (as determined by the headers I send back from the server).

Do I have to call something fancy with NSURLConnection? How can I get the iphone to use the cached version of the url?

Update: Here is a link to my code

http://pastie.org/808549

回答1:

I think you may need to add a "cachePolicy" to your NSURLRequest:

The NSURLRequestReturnCacheDataElseLoad cache policy will cause the URL loading system to use cached data ignoring its age or expiration date, if it exists, and load the data from the originating source only if there is no cached version.

http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/URLLoadingSystem/Concepts/CachePolicies.html#//apple_ref/doc/uid/20001843

There's a few different policies there. Perhaps one of them will help.

回答2:

The answer is, unfortunately, that the iPhone can't do disk caching with NSURLCache, making it inappropriate for the scenario I outlined.

I'm rolling my own class.

回答3:

Take a look at the ASI classes while you're at it.

http://allseeing-i.com/ASIHTTPRequest/

They are pretty nice.

回答4:

Caching with the policies as described by @typeoneerror seems to work fine if you're using etags in your requests.