title: Make GMSCircle respond to tap?
body: <p>I am using the Google Maps API for iOS and I want to make it so when you tap on a GMSCircle it pops up a little thing I coded elsewhere. I have set the circle to "tappable" but I cannot find what I need to set or make to listen for the tap. What do I use?</p>
  
  <pre><code>    CLLocationCoordinate2D circleCenter = CLLocationCoordinate2DMake(10,10);
  GMSCircle *circ = [GMSCircle circleWithPosition:circleCenter
                                           radius:10];
  circ.tappable = true;
  [circ setFillColor:[UIColor colorWithRed:1 green:0 blue:0 alpha:.5]];
  
  circ.map = mapView_;
  </code></pre>