multiple goals handling in actionlib, unable to compare goal_handle

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Greetings

I am trying to implement an action server which can handle multiple goal request from multiple clients. I read wiki actionlib and realized SimpleActionServer is not sufficient. I am implementing an ActionServer class object. An ActionClient object sends multiple goals to the ActionServer. Since there is no goal-id attached, I need to remember goal-handle object (ClienGoalHandle class) for each of the send goals. I realized that compiler complains about comparing of the goal-handle object, Although I can check for equality between goal-handles.

Is there a known way to use goal-handle or its derivatives, as key for containers such as STL::map or multi-maps etc? else I will end up using a vector and sequential searches for bookkeeping data.

It will greatly help me in managing bookkeeping activities. In my task, client can send multiple goals to the server. Server sends these goals further to different robots. I need to maintain goal-handles for management of post-server-response activities.

Is there any document tutorial or library showing functionality of non-Simple ActionServer/ActionClient?

Is it possible to have multiple goal handles result in single transition callback?

Rgds