question about tutorial "Setting Velocity on Joints and Links"

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hi friends. ubuntu 16 + gazebo 7， I am folowing the tutorial "Setting Velocity on Joints and Links"

I download the source files in here, the cmake is ok, but make is wrong, it said: "class gazebo::physics::Model’ has no member named ‘CreateLink’", full:

> In file included from /home/mw/Downloads/set_vel_plugin/src/SetLinkVelocityPlugin.cpp:21:0:
/home/mw/Downloads/set_vel_plugin/include/ode_perfect_velocity.hh: In member function ‘void gazebo::OdePerfectVelocityController::Start(gazebo::physics::LinkPtr, gazebo::math::Vector3, gazebo::math::Vector3, double, double)’:
/home/mw/Downloads/set_vel_plugin/include/ode_perfect_velocity.hh:36:36: error: ‘class gazebo::physics::Model’ has no member named ‘CreateLink’
         this->phantomLink = model->CreateLink("__perfect_phantom_link__");
                                    ^
CMakeFiles/SetLinkVelocityPlugin.dir/build.make:62: recipe for target 'CMakeFiles/SetLinkVelocityPlugin.dir/src/SetLinkVelocityPlugin.cpp.o' failed
make[2]: *** [CMakeFiles/SetLinkVelocityPlugin.dir/src/SetLinkVelocityPlugin.cpp.o] Error 1
CMakeFiles/Makefile2:104: recipe for target 'CMakeFiles/SetLinkVelocityPlugin.dir/all' failed
make[1]: *** [CMakeFiles/SetLinkVelocityPlugin.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

so what is the problem? thanks