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Porting nodes to nodelets

Work in progress...(see nodelet_tutorial_math for an example)

• add the necessary #includes
• get rid of int main()
• subclass nodelet::Nodelet
• move code from constructor to onInit()
• add the PLUGINLIB_EXPORT_CLASS macro

• add <build_depend> and <run_depend> dependencies on nodelet in the package manifest.

• add the <nodelet> item in the <export> part of the package manifest

• create the .xml file to define the nodelet as a plugin
• make the necessary changes to CMakeLists.txt (comment out a rosbuild_add_executable, add a rosbuild_add_library)

Minimal Nodelet

MyNodeletClass.h

Here we define the Class of our Nodelet. It's a good practice to place the header file under include/package_name/.

NB: The usage of the namespace is a good practice but not mandatory, in the following example we will proceed with the namespace example_pkg

#include <nodelet/nodelet.h>

namespace example_pkg
{

    class MyNodeletClass : public nodelet::Nodelet
    {
        public:
            virtual void onInit();
    };

}

MyNodeletClass.cpp

This file should be placed under the src/ folder of your actual package

// this should really be in the implementation (.cpp file)
#include <pluginlib/class_list_macros.h>

// Include your header
#include <example_pkg/MyNodeletClass.h>

// watch the capitalization carefully
PLUGINLIB_EXPORT_CLASS(example_pkg::MyNodeletClass, nodelet::Nodelet)

namespace example_pkg
{
    void MyNodeletClass::onInit()
    {
        NODELET_DEBUG("Initializing nodelet...");
    }
}

nodelet_plugins.xml

This file should be placed along with the package.xml file

<library path="lib/libMyNodeletClass">
  <class name="example_pkg/MyNodeletClass" type="example_pkg::MyNodeletClass" base_class_type="nodelet::Nodelet">
  <description>
  This is my nodelet.
  </description>
  </class>
</library>

package.xml

...
<build_depend>nodelet</build_depend>
<run_depend>nodelet</run_depend>
<export>
  <nodelet plugin="${prefix}/nodelet_plugins.xml" />
</export>
...

mynodelet.launch

Launch file should be placed under the launch/ repertory of your package, you can create it if it does not exist.

<launch>
  <node pkg="nodelet" type="nodelet" name="standalone_nodelet"  args="manager" output="screen"/>

  <node pkg="nodelet" type="nodelet" name="MyNodeletClass" args="load example_pkg/MyNodeletClass standalone_nodelet" output="screen">
  </node>
</launch>