[ros-users] roslua: creating messages with subtypes

[Steven Bellens]

2011/2/21 Markus Klotzbuecher <markus.klotzbuecher at mech.kuleuven.be>:
> Dear List,
>
> I just gave roslua a try and its working quite nicely. One smaller
> problem I noticed is when printing some array types:
>
> $ lua -lroslua
> Lua 5.1.4  Copyright (C) 1994-2008 Lua.org, PUC-Rio
>> twist = roslua.get_msgspec("geometry_msgs/Twist")
>> t=twist:instantiate()
>> t:print()
> geometry_msgs/Twist
> /home/mk/src/git/lua/roslua/src/roslua/msg_spec.lua:53: attempt to call method 'find' (a nil value)
> stack traceback:
>      /home/mk/src/git/lua/roslua/src/roslua/msg_spec.lua:53: in function 'is_array_type'
>      /home/mk/src/git/lua/roslua/src/roslua/message.lua:259: in function 'print_value'
>      /home/mk/src/git/lua/roslua/src/roslua/message.lua:285: in function 'print'
>      stdin:1: in main chunk
>      [C]: ?
>>
>
> Secondly I wondered if there is a more compact way to create messages
> which contain submessages. For instance to create and fill a
> "geometry_msgs/Twist" I did the following:
>
> local Vector3=roslua.get_msgspec("geometry_msgs/Vector3")
>
> local m = p.msgspec:instantiate() -- geometry_msgs/Twist message
> local vec3lin = Vector3:instantiate()
> local vec3ang = Vector3:instantiate()
>
> vec3lin.values.x=x
> vec3lin.values.y=y
> vec3lin.values.z=z
> vec3ang.values.x=xang
> vec3ang.values.y=yang
> vec3ang.values.z=zang
>
> m.values.linear = vec3lin
> m.values.angular = vec3ang
>
>
> Before that I tried
>
> m.values.linear.x = x
> m.values.linear.y = y
> ...
>
> but this didn't work.

What is the 'values' for?
How about

m.linear.x = x
m.linear.y = y   ?

Steven

>
> Thanks in advance!
>
>   Markus
>
>
>
>
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