IOS 清除UIWebview的缓存以及cookie

cookie清除  
            NSHTTPCookie *cookie;
            NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
            for (cookie in [storage cookies])
            {
                [storage deleteCookie:cookie];
            }

 缓存  清除
            [[NSURLCache sharedURLCache] removeAllCachedResponses];