[roscpp] Get package name from argv vector

edit

Hello everyone,

as per the title of the post, I am looking for a method able to get the package name from the argv vector inside my ROS node implementation, bearing in mind that it is my plan to always use the roslaunch utility to run the executable.

As far as I have seen, roslaunch converts the line of the launch file:

<node pkg="pkg_name" type="exec_name" name="node_name"/>

into the command:

path-to-catkin-ws/devel/lib/pkg_name/exec_name __name:=node_name

which is then used to build the argv parameters vector. Is there any other way to get the package name other than extracting it from the string contained in argv[0]?

EDIT

I'll try to explain briefly the reason why I need this. My working group is in the process of refactoring some code in our system. In particular, we have two packages, say base_pkg and derived_pkg, where the latter depends on the former.

The package base_pkg provides a library containing a class, say MyROSNodeInterface, which defines the interface for the ROS nodes we are developing in our system. The package derived_pkg contains a class, say MyROSNode, which implements an actual ROS node inheriting from the MyROSNodeInterface class.

The MyROSNodeInterface class implements some functionalities that we want all the actual nodes to have in common, so we want to be able to have access to information about the derived class, such as the package name, in the base one.

In the legacy version of the code, these functionalities were implemented in the header file of the class MyROSNodeInterface using ROS defines such as ROS_PACKAGE_NAME. This file was then included in the file MyROSNode.h and compiled when compiling the package derived_pkg. In this case everything worked fine, as the compile-time constants assumed the values specified in the compilation of derived_pkg, e.g. ROS_PACKAGE_NAME=derived_pkg.

Now, we want to refactor the implementation of the class MyROSNodeInterface in header file and implementation file. In this case, the compile-time constants will be used in the MyROSNodeInterface.cpp file, which will only be compiled when the base_pkg is compiled. In this case, the compile-time constants will assume the values given during the compilation of base_pkg, e.g. ROS_PACKAGE_NAME=base_pkg.

The only way that came to my mind to solve this problem is to add the all the additional information about the actual node, such as the package name, in the interface of the MyROSNodeInterface class, but this would require a change in the code of MyROSNode (and all the other actual nodes) to pass an additional parameter to the base class constructor. Since at the moment the interface of the class MyROSNodeInterface is the following:

class MyROSNodeInterface {
    MyROSNodeInterface(int argc, char **argv, const std::string& node_name);

    // Other interface methods
};

I was wondering whether it is possible to retrieve at least the package name from the argv vector.

I hope this helps to understand better the problem.