title: Adding waypoint in ns3 for waypoint mobility model
body: <p>I was trying adding waypoints for waypoint mobility model but i am not able to do so. This is what I did</p>
  
  <pre><code>Ptr&lt;WaypointMobilityModel&gt; waypoints = CreateObject&lt;WaypointMobilityModel&gt; (); 
  waypoints-&gt;AddWaypoint (Waypoint (Seconds (2.0),Vector (25.0, 0, 0))); 
  waypoints-&gt;AddWaypoint (Waypoint (Seconds (5.0),Vector (50.0, 0, 0))); 
  mobility.SetMobilityModel(waypoints);  //mobility is my MobilityHelper
  </code></pre>
  
  <p>SetMobilityModel expects a string but is instead getting a ptr when is called with parameter waypoints. Could you tell what should be the correct way for doing so?</p>
  
  <p>This is the error i got:</p>
  
  <pre><code>no matching function for call to ‘ns3::MobilityHelper::SetMobilityModel(ns3::Ptr&lt;ns3::WaypointMobilityModel&gt;&amp;)’
   mobility.SetMobilityModel(waypoints);
   note:   no known conversion for argument 1 from ‘ns3::Ptr&lt;ns3::WaypointMobilityModel&gt;’ to ‘std::string {aka std::basic_string&lt;char&gt;}’
  </code></pre>