class gazebo::physics::World’ has no member named ‘GetModel’; did you mean ‘Models’?

edit

This is the API documentation for Gazebo 9. The method you are looking for is ModelByName(name).

reaction to the EDIT

The use of the API looks right. One thing that comes on my mind is that the retrieval of the ball model is happening right after the call for the model insertion into the world. Is it possible the model is still being loaded when you want to get the pointer to it?

What happens if you wait until the model is fully loaded? Something like

class SimulatorPlugin : public WorldPlugin
{
    void Load(physics::WorldPtr _world, sdf::ElementPtr _sdf)
    {
        sdf::SDF ballSDF;
        ballSDF.SetFromString(
        "<sdf version ='1.6'>\
                <model name='ball'>\
                    <pose>0 0 0 0 0 0</pose>\
                        <include>\
                            <uri>/home/peter/gazebo_plugin/models/my_robocup_spl_ball</uri>\
                        </include>\
                </model>\
            </sdf>");

        sdf::ElementPtr ballmodel = ballSDF.Root()->GetElement("model");
        ballmodel->GetAttribute("name")->SetFromString("ball");
        _world->InsertModelSDF(ballSDF);

        physics::ModelPtr ballmodelPtr = _world->ModelByName("ball");

        while(ballmodelPtr == NULL) 
        {
             ballmodelPtr = _world->ModelByName("ball");
        }
        printf("ball found \n");

        _world->LoadPlugin("librifball.so", "rifball", ballmodel);
    }
}

EDIT 2

The solution to wait for the model to be loaded showed above cannot work. The while loop inside the Load function would block all the other processes so the model or anything else would not be loaded ever.

See this answer for the correct solution: https://answers.gazebosim.org/questio...