Update Pluginlib.rst (ros2#5894)

Signed-off-by: Christoph Fröhlich <[email protected]>

Author: christophfroehlich

source/Tutorials/Beginner-Client-Libraries/Pluginlib.rst

@@ -73,43 +73,17 @@ The code above creates an abstract class called ``RegularPolygon``.
 One thing to notice is the presence of the initialize method.
 With ``pluginlib``, a constructor without parameters is required, so if any parameters to the class are needed, we use the initialize method to pass them to the object.
 
-We need to make this header available to other classes, so open ``~/ros2_ws/src/polygon_base/CMakeLists.txt`` for editing.
-Add the following lines after the ``target_link_libraries`` command:
-
-.. code-block:: cmake
-
-    install(
-      DIRECTORY include/
-      DESTINATION include
-    )
-
-And add this command before the ``ament_package`` command:
-
-.. code-block:: cmake
-
-    # Export old-style CMake variables
-    ament_export_include_directories(
-      include
-    )
-    ament_export_libraries(
-      ${PROJECT_NAME}
-    )
-
-    # Export modern CMake targets
-    ament_export_targets(
-      export_${PROJECT_NAME}
-    )
-
-We need to make this library available to other packages, so open ``~/ros2_ws/src/polygon_base/CMakeLists.txt`` for editing.
-Add the following lines after the ``find_package(pluginlib REQUIRED)`` command:
+We need to make this header available to other classes by exporting it as an interface library.
+To do so, open ``~/ros2_ws/src/polygon_base/CMakeLists.txt`` for editing
+and add the following lines after the ``find_package(pluginlib REQUIRED)`` command:
 
 .. code-block:: cmake
 
     # Library (this will be used as the base class for plugins)
-    add_library(${PROJECT_NAME} SHARED src/area_node.cpp)
+    add_library(${PROJECT_NAME} INTERFACE)
     add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
-    target_compile_features(${PROJECT_NAME} PUBLIC c_std_99 cxx_std_17)
-    target_include_directories(${PROJECT_NAME} PUBLIC
+    target_compile_features(${PROJECT_NAME} INTERFACE c_std_99 cxx_std_17)
+    target_include_directories(${PROJECT_NAME} INTERFACE
       $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
       $<INSTALL_INTERFACE:include/${PROJECT_NAME}>
     )
@@ -132,6 +106,20 @@ Add the following lines after the ``find_package(pluginlib REQUIRED)`` command:
       DESTINATION share/${PROJECT_NAME}/cmake
     )
 
+And add this commands before the ``ament_package`` command:
+
+.. code-block:: cmake
+
+    # Export old-style CMake variables
+    ament_export_include_directories(
+      include
+    )
+
+    # Export modern CMake targets
+    ament_export_targets(
+      export_${PROJECT_NAME}
+    )
+
 We will return to this package later to write our test node.
 
 2 Create the Plugin Package