title: Waiting on asynchronous methods using NSCondition
body: <p>I am downloading four plist files asynchronously over the internet. I need to wait until all four files are downloaded, until I either on the first run, push a UIViewController, or on all subsequent runs, refresh the data, and reload all my UITableViews.</p>
  
  <p>On the first run, everything works perfectly. When refreshing though, all four url requests are called, and started, but never call their completion or failure blocks, and the UI freezes. Which is odd since I preform all operations in a background thread. I have not been able to figure out why this is happening.</p>
  
  <p>The first load and the refresh methods call the four "update" methods in the same way, and use NSCondition in the same way.</p>
  
  <p>For the first run:</p>
  
  <pre><code>- (void)loadContentForProgram:(NSString *)programPath
  {
      NSLog(@"Start Load Program");
      AppDelegate *myDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
      hud = [[MBProgressHUD alloc] initWithView:myDelegate.window];
      [myDelegate.window addSubview:hud];
      hud.labelText = @"Loading...";
      hud.detailsLabelText = @"Loading Data";
      dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
          //Do stuff here to load data from files
  
          //Update From online files
          hud.detailsLabelText = @"Updating Live Data";
          resultLock = NO;
          progressLock = NO;
          recallLock = NO;
          stageLock = NO;
  
          condition = [[NSCondition alloc] init];
          [condition lock];
  
          [self updateCurrentCompsText];
          [self updateCompetitionResults];
          [self updateCompetitionRecalls];
          [self updateCompetitionProgress];
  
  
          while (!resultLock) {
              [condition wait];
          }
          NSLog(@"Unlock");
          while (!stageLock) {
              [condition wait];
          }
          NSLog(@"Unlock");
          while (!recallLock) {
              [condition wait];
          }
          NSLog(@"Unlock");
          while (!progressLock) {
              [condition wait];
          }
          NSLog(@"Unlock");
          [condition unlock];
          updateInProgress = NO;
          //Reset Refresh controls and table views
          self.refreshControlsArray = [[NSMutableArray alloc] init];
          self.tableViewsArray = [[NSMutableArray alloc] init];
          NSLog(@"Finished Loading Program");
          [[NSNotificationCenter defaultCenter] postNotificationName:@"WMSOFinishedLoadingProgramData" object:nil]; //Pushes view controller
          dispatch_async(dispatch_get_main_queue(), ^{
              [MBProgressHUD hideHUDForView:myDelegate.window animated:YES];
          });
      });
  }
  </code></pre>
  
  <p>When refreshing data:</p>
  
  <pre><code>- (void)updateProgramContent
  {
      if (!updateInProgress) {
          updateInProgress = YES;
          for (int i = 0; i &lt; self.refreshControlsArray.count; i++) {
              if (!((UIRefreshControl *)self.refreshControlsArray[i]).refreshing) {
                  [self.refreshControlsArray[i] beginRefreshing];
                  [self.tableViewsArray[i] setContentOffset:CGPointMake(0.0, 0.0) animated:YES];
              }
          }
  
          resultLock = NO;
          stageLock = NO;
          recallLock = NO;
          progressLock = NO;
          dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
  
              condition = [[NSCondition alloc] init];
              [condition lock];
  
              [self updateCompetitionProgress];
              [self updateCompetitionRecalls];
              [self updateCompetitionResults];
              [self updateCurrentCompsText];
  
              while (!resultLock) {
                  [condition wait];
              }
              NSLog(@"Unlock");
              while (!stageLock) {
                  [condition wait];
              }
              NSLog(@"Unlock");
              while (!recallLock) {
                  [condition wait];
              }
              NSLog(@"Unlock");
              while (!progressLock) {
                  [condition wait];
              }
              NSLog(@"Unlock");
              [condition unlock];
          });
  
          for (int i = 0; i &lt; self.refreshControlsArray.count; i++) {
              [self.refreshControlsArray[i] performSelector:@selector(endRefreshing) withObject:nil afterDelay:1.0];
              [self.tableViewsArray[i] performSelector:@selector(reloadData) withObject:nil afterDelay:1.0];
          }
          updateInProgress = NO;
      }
  }
  </code></pre>
  
  <p>The block below that appears in each loading method above, corresponds to a method that will download and update a specific piece of data.</p>
  
  <pre><code>[self updateCompetitionProgress];
  [self updateCompetitionRecalls];
  [self updateCompetitionResults];
  [self updateCurrentCompsText];
  </code></pre>
  
  <p>which runs:</p>
  
  <pre><code>- (void)updateCompetitionResults
  {
      __block NSDictionary *competitionResultsData = nil;
      NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"Some URL",[self.programName stringByReplacingOccurrencesOfString:@" " withString:@"%20"]]] cachePolicy:NSURLCacheStorageNotAllowed timeoutInterval:20.0];
      AFPropertyListRequestOperation *operation = [AFPropertyListRequestOperation propertyListRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id propertyList) {
          competitionResultsData = (NSDictionary *)propertyList;
          [competitionResultsData writeToFile:[@"SOME LOCAL PATH"] atomically:NO];
          [self updateCompetitionResultsWithDictionary:competitionResultsData];
      } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id propertyList) {
          competitionResultsData = [NSDictionary dictionaryWithContentsOfFile:[@"SOME LOCAL PATH"]];
          NSLog(@"Failed to retreive competition results: %@", error);
          [self updateCompetitionResultsWithDictionary:competitionResultsData];
      }];
      [operation start];
  }
  </code></pre>
  
  <p>and the completion and failure blocks call the same method to update the data</p>
  
  <pre><code>- (void)updateCompetitionResultsWithDictionary:(NSDictionary *)competitionResultsData
  {
      //Do Stuff with the data here
      resultLock = YES;
      [condition signal];
  }
  </code></pre>
  
  <p>So, Why does this work on the first run, but not any of the subsequent runs?</p>