title: Creating and canceling an NSURLConnection
body: <p>I have a NSURLConnection that is working fine when I allow the load to complete.  But if the user hits the back button, meaning the webview will dissappear, I want to cancel the NSURLConnection in progress. But if have the webview call into this class when viewWillDissapear is called, and then I do:</p>
  
  <pre><code>[conn cancel]
  </code></pre>
  
  <p>I get an NSINValidArgument exception.  </p>
  
  <p>The connection is defined as instance data in the .h file as:</p>
  
  <pre><code>NSURLConnection *conn;
  </code></pre>
  
  <p>The async is initiated here:</p>
  
  <pre><code>NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:articleURL]];
  
      if ([NSURLConnection canHandleRequest:request] &amp;&amp; reachable) {
          // Set up an asynchronous load request
          conn = [NSURLConnection connectionWithRequest:request delegate:self];
          loadCancelled = NO;
          if (conn) {
              NSLog(@" ARTICLE is REACHABLE!!!!");
              self.articleData = [NSMutableData data];
          }
      }
  </code></pre>