fix template path in message generator

ros2model/api/model_generator/message_generator.py

@@ -19,17 +19,32 @@
 import ros2model.core.metamodels.metamodel_ros as ROSModel
 import logging
 from devtools import pprint
+from ament_index_python import get_package_share_directory
 
 Template_Folder = Path(__file__).parent.resolve() / "templates"
 Template = Path(Template_Folder / "message.ros.j2")
 
+try:
+    from ament_index_python import get_package_share_directory
+
+    Template_Folder_ROS = Path(get_package_share_directory("ros2model") + "/templates")
+    Template_ROS = Path(Template_Folder_ROS / "component.ros2.j2")
+except ImportError:
+    Template_ROS = None
+
 
 class MessageGenerator(GeneratorCore):
     def __init__(self, template_path=None) -> None:
         if template_path != None:
             self.template_path = Path(template_path).resolve()
-        else:
+        elif Template_ROS != None and Template_ROS.is_file():
             self.template_path = Template
+        elif Template.is_file():
+            self.template_path = Template
+        else:
+            raise FileNotFoundError(
+                f"Can't find template either from {Template.absolute().as_posix()} or {Template_ROS.absolute().as_posix()}"
+            )
         super().__init__(self.template_path, ".ros")
 
     def generate_a_package(self, rosmodel: ROSModel.Package, output_dir: str):