RAC example

   [[[[[[[[[RACAbleWithStart(client, networkReachabilityStatus)
           filter:^BOOL(NSNumber* statusNumber) {
                AFNetworkReachabilityStatus status = statusNumber.intValue;
                BOOL autoLoadOn3G = [[NSUserDefaults standardUserDefaults] boolForKey:KEY_AUTOLOAD_3G];
                
                return (status == AFNetworkReachabilityStatusReachableViaWiFi
                        || (autoLoadOn3G && status == AFNetworkReachabilityStatusReachableViaWWAN));
            }]
            take:1]
            flattenMap: ^(id value){
                return [client rac_getModelOfClass:PFMProgram.class fromPath:@"getSubscribePrograms" params:@{}];
            }]
            flattenMap:^RACStream *(NSArray *programs) {
                return programs.rac_sequence.signal;
            }] doNext:^(PFMProgram *program) {
                int newPodcasts = program.countPodcasts - program.numOfPodcastsAtLastSync;
                ((NSMutableDictionary*)self.lastSyncCount)[@(program.programId)] = @(newPodcasts);
                
            }]
            flattenMap:^RACStream *(PFMProgram *program) {
                int autoLoadNum = [[NSUserDefaults standardUserDefaults] integerForKey:KEY_AUTOLOAD_NUMBER];
                if (autoLoadNum == 0) { autoLoadNum = 3; }
                
                int newPodcasts = program.countPodcasts - program.numOfPodcastsAtLastSync;
                int limit = MIN(autoLoadNum, newPodcasts);

                program.numOfPodcastsAtLastSync = program.countPodcasts;
                
                if (limit > 0) {
                    NSLog(@"Downloading %d last issues for program %@", limit, program.name);
                    return [client rac_getModelOfClass:PFMPodcast.class fromPath:@"getPodcastsByProgram" params:@{@"id": @(program.programId), @"limit":@(limit)}];
                } else {
                    NSLog(@"No last issues for program %@", program.name);
                    return [RACSignal empty];
                }
            }]
            flattenMap:^RACStream *(NSArray *podcasts) {
                return podcasts.rac_sequence.signal;
            }]
            doError:^(NSError *error) {
                handleError(error);
            }]
            subscribeNext:^(PFMPodcast *podcast) {
                [[PFMDownloadManager manager] enqueuePodcast:podcast];
            }];