title: Check if NSTimer selector has finished working
body: <p>I am calling a service method in <code>NSTimer</code> after every 3 seconds. However before each time that method is being called, I want to check if previous one in timer is complete or not. I have done following which is not resulting in success.</p>
  
  <pre><code>timer = [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(CallParseOperation) userInfo:nil repeats:YES]; 
  </code></pre>
  
  <p><strong>CheckOperation</strong>:  </p>
  
  <pre><code>-(void)CheckOperation{
  
      if([Data getInstance].kOperation == TRUE)
      {
          [self CallParseOperation];
      }
  
  }
  </code></pre>
  
  <p><strong>CallParseOperation</strong>:  </p>
  
  <pre><code>-(void)CallParseOperation{
  
  
      [Data getInstance].kOperation = FALSE;
      operationQueue=[[NSOperationQueue alloc] init];
      ParseOperation *obj=[[ParseOperation alloc] initWithMembers:ID];
      NSInvocationOperation *reloadOp = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(tableReload) object:nil];
      [reloadOp addDependency:obj];
      [operationQueue addOperation:obj];
      [operationQueue addOperation:reloadOp];
      //[operationQueue waitUntilAllOperationsAreFinished];
      [obj release];
      [reloadOp release];
  
  } 
  </code></pre>
  
  <p>Somewhere at the end of this implementation I am setting this <code>bool</code> as <code>TRUE</code>. But this is not working. The control is just stuck inside this timer.  </p>