Fix getParam returned value

[knuesel]

Hi, thanks for making this package! This PR fixes an error I get when runningdartros_example.dart:

Unhandled exception:
type 'Future<dynamic>' is not a subtype of type 'Future<String>'
#0      RosXmlRpcClient.getMasterUri (package:dartros/src/ros_xmlrpc_client.dart:330:36)
#1      NodeHandle.getMasterUri (package:dartros/src/node_handle.dart:30:41)
#2      main (file:///home/j/codiman/rosclient/dartros/example/dartros_example.dart:5:12)

It also fixes a similar error in lookupNode, and makes the example's output a bit clearer by setting the parameter to a non-default value.

I wanted to add a test, but I can't get the code to run in the latest version, I think there's a commit missing in std_msgs_dart, adding the $prototype variable?

[TimWhiting]

Hi, I wasn't aware of anyone besides my research lab using this. Thanks for the feedback and the PR. Tested it locally and it worked. I'll try adding tests later. I just updated yesterday to use a new message generation format. Now, I'm using the prototype variable. Maybe try doing a pub upgrade and making sure that you have version 0.0.3 of std_msgs? Sorry I don't have much documentation yet. My priority has just been to get it working well. Hope you were able to figure out the message generation for your own project.

[TimWhiting]

@knuesel Just published 0.0.4+3 with the fix.

[knuesel]

Thanks for the quick merge! That will make it two labs then :) (I'm in the initial stage of research project that will use Flutter and ROS).

For std_msgs I think there's a commit that hasn't been pushed, the master branch still has version 0.0.2: https://github.com/TimWhiting/std_msgs_dart/blob/master/pubspec.yaml

[TimWhiting]

Cool, I'll fix the std_msgs master branch. But you should be able to use the version on pub.dev: https://pub.dev/packages/std_msgs

[TimWhiting]

@knuesel Also, for your information if you add this ros package to your workspace it should generate dartros messages for all of your custom messages: https://github.com/TimWhiting/gendart

[knuesel]

Ah sorry I didn't realize that pub.dev could have a more recent version than GitHub. Thanks for the pointer to gendart.

[TimWhiting]

Yes, there are a few message packages that I had to publish to pub.dev since they are depended on by dartros itself. I'm currently debating whether to also publish sensor_msgs, and geometry_msgs since they are widely used.

[TimWhiting]

I'm going to add a few issues about documentation for this. Feel free to contribute documentation in places where something is not obvious. I know most people are coming from a rospy or roscpp background, and this is based more off of rosnodejs.

Updated:
Issues: #5 #4

[knuesel]

I'll see what it takes to make this work with my project and update the documentation accordingly (although the project uses actions so it might be a while before it runs?)