title: How to set up HTTP connection in a special class?
body: <p>I want to create a class to handle all the HTTP connection work for other classes(in order to avoid writing codes repeatedly). 
  I call it ConnectionCenter(subclass of NSObject) and add the following codes to it:</p>
  
  <pre><code>-(void)connect:(NSString *)strURL obj:(ConnectCenter *)objConnect
  {
      NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:strURL]
                                                cachePolicy:NSURLRequestUseProtocolCachePolicy
                                            timeoutInterval:60.0];
  
      NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:objConnect];
      if (theConnection) 
      {
          // receivedData is declared as a method instance elsewhere
          receivedData = [[NSMutableData data] retain];
      } 
      else 
      { 
          // inform the user that the download could not be made
      }
  
  }
  
  - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
  {
      // append the new data to the receivedData
      // receivedData is declared as a method instance elsewhere
      [receivedData appendData:data];
  }
  </code></pre>
  
  <p>And other classes call it by passing a URL and an object of ConnectionCenter. But the method 'didReceiveData' in ConnectionCenter is not called. Any ideas about what's the problem with it?</p>