modifications to enqueueOperation

gistfile1.m

-(void) enqueueOperation:(MKNetworkOperation*) operation forceReload:(BOOL) forceReload {
    dispatch_queue_t originalQueue = dispatch_get_current_queue();
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [operation setCacheHandler:^(MKNetworkOperation* completedCacheableOperation) {
            
            // if this is not called, the request would have been a non cacheable request
            //completedCacheableOperation.cacheHeaders;
            NSString *uniqueId = [completedCacheableOperation uniqueIdentifier];
            [self saveCacheData:[completedCacheableOperation responseData] 
                         forKey:uniqueId];
            
            [self.cacheInvalidationParams setObject:completedCacheableOperation.cacheHeaders forKey:uniqueId];
        }];
        
        double expiryTimeInSeconds = 0.0f;    
        
        if(!forceReload) {
            NSData *cachedData = [self cachedDataForOperation:operation];
            if(cachedData) {
                dispatch_async(originalQueue, ^{
                    [operation setCachedData:cachedData];                    
                });

                
                NSString *uniqueId = [operation uniqueIdentifier];
                NSMutableDictionary *savedCacheHeaders = [self.cacheInvalidationParams objectForKey:uniqueId];
                // there is a cached version.
                // this means, the current operation is a "GET"
                if(savedCacheHeaders) {
                    NSString *expiresOn = [savedCacheHeaders objectForKey:@"Expires"];
                    NSDate *expiresOnDate = [NSDate dateFromRFC1123:expiresOn];
                    expiryTimeInSeconds = [expiresOnDate timeIntervalSinceNow];
                    
                    [operation updateOperationBasedOnPreviousHeaders:savedCacheHeaders];
                }
            }
        }
        
        NSUInteger index = [_sharedNetworkQueue.operations indexOfObject:operation];
        if(index == NSNotFound) {
            
            if(expiryTimeInSeconds <= 0)
                [_sharedNetworkQueue addOperation:operation];
            else if(forceReload)
                [_sharedNetworkQueue addOperation:operation];
            // else don't do anything
        }
        else {
            // This operation is already being processed
            MKNetworkOperation *queuedOperation = (MKNetworkOperation*) [_sharedNetworkQueue.operations objectAtIndex:index];
            [queuedOperation updateHandlersFromOperation:operation];
        }
        
        if([self.reachability currentReachabilityStatus] == NotReachable)
            [self freezeOperations];
    });
}