@Karsten1987 I've updated the examples to be more in line with the new composition model. Please take another look (thanks!).

@mjcarroll Thanks for the review!

In the spirit of keeping the examples in this package minimal, I'd prefer not to make these actual components and bring in a dependency to rclcpp_component. They are really examples of action clients/servers that use member functions, though I've tried to set them up so they could easily be ported to be components. I think it would be better to add a components version to demos or even examples/rclcpp/minimal_composition.

I'll just add that, our long term goal has been to use composition everywhere, and make things that have their own main as the "exceptional cases". However, I can see an argument for not doing this just here, but instead leaving this pr as-is and then updating all the examples at once.

This is probably a topic we should discuss at some point before the release...

@jacobperron This is still not fully composable. Each node has to be its own library and the node has to be registered with the class loader macro

#include "rclcpp_components/register_node_macro.hpp"
RCLCPP_COMPONENTS_REGISTER_NODE(MinimalActionClient)

as well as added to the ament index within the cmake context:

rclcpp_components_register_nodes(action_client_member_functions "MinimalActionClient")

Also, in order to support manual composition - besides the command line tool via ros2 component - I think it makes sense to separate the node library in a .hpp and .cpp.

Based on our offline discussion, I'll leave these examples as not fully composable and create a follow-up PR to add composable examples to the demos repo.

I still need to update this PR based on the changes in ros2/rclcpp#701.

Ready for another round of review.

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