[ros-users] New Parameter Server

[Dave Hershberger]

+1 on the project, I'm glad to see this getting attention!

For the Qt version of rviz, I wrote a property hierarchy system in C++
which I have been fairly happy with.

For example usage, see map_display.cpp:
https://github.com/ros-visualization/rviz/blob/groovy-devel/src/rviz/default_plugin/map_display.cpp

That system uses Qt slots to receive notice of property changes when
needed. (If Qt is undesirable you could probably go with Boost slots or
even just member function pointers.)

The bit about rviz's property API that is perhaps unique is that the
Property object actually owns the data.  That means any time you want one
of the property values you say something like "width_property_->getInt()"
or "name_property_->getString()".  What is returned by the Property object
is always the latest value.  If you need to learn about updates, you don't
need any parameters coming through the update function, because you can
just ask the parameter object for the latest value from inside the update
function.  This felt simpler to me than requiring API users to implement
get/set functions for every parameter, which is how it had been implemented
before.

Dave


On Wed, Apr 17, 2013 at 12:43 PM, Thibault Kruse <kruset at in.tum.de> wrote:

> I found my draft rep, and now put it on github:
> https://github.com/tkruse/rep/**blob/nodeparam/nodeparam-REP.**rst<https://github.com/tkruse/rep/blob/nodeparam/nodeparam-REP.rst>
>
> Note this was work in progress when I stopped working on it.
>
> Other things I considered back then:
> - whether to support complex parameter types like poses (rather than just
> primitive values)
> - how to organize parameter naming (I think there were some
> inconsistencies between rospy and roscpp around the '~')
> - using the same system for logger levels
> - grouping of parameters instead of having flat lists
> - whether to support batch updates of multiple parameters as one operation
> (e.g. when parameter validation would else deadlock changing two
> interdependent parameters)
>
> cheers,
>   Thibault
>
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