Action.sendGoal(): Why is resultCallback required?

[ikwilnaarhuisman]

Hi! Right now I'm working on implementing a Charge Action, when I want my robot to charge I send it a goal using this Action. This works great, but I'm forced to define a resultCallback. The thing is that I use a different topic to determine whether the robot went to charge or not. So I don't have any use for the callback on this Goal.

I'm just wondering why resultCallback isn't allowed to be undefined like feedbackCallback and feedbackCallback?

[EzraBrooks]

In callback-oriented programming, it's pretty normal to have a required callback to make it clear via the function signature that a particular function is callback-oriented, even if it's a callback some people might exclude. It's perfectly valid to just pass () => {} if you deliberately want to do nothing.

However, I might advise you to change your design of your Action! It sounds like you might be setting yourself up for some synchronization pain later. Personally, if I was setting up an Action that "tells the robot to go charge", I would have the Action's feedback indicate how far into the charging process it is, and the result type return that the charging completed successfully or unsuccessfully.