callback function with arguments from subscription to three nodes
Hi !
I'm looking for a way to process a
sensor_msgs::LaserScan
using two angles provided by another node that provides two topics (the angles as std_msgs::Float32). The thing is, when I read other posts regarding sending several parameters to a callback function (boost::bind) or using one callback function for several subscriptions (this case seems to be only explained for cases where you want to apply a similar function to three different topics independently, and not somehow combine the three topics to build something to publish, which is what I want to do), it never really answers all of my questions.
I'm therefore looking for something like:
pub_ = nh_.advertise<sensor_msgs::LaserScan>("/filtered_scan",100);
sub_ = nh_.subscribe<sensor_msgs::LaserScan>("/scan",100, &SubscribeAndPublish::callbackFilter, this);
sub2_ = nh_.subscribe<std_msgs::Float32>("/angle1",100, &SubscribeAndPublish::callbackFilter, this);
sub3_ = nh_.subscribe<std_msgs::Float32>("/angle2",100, &SubscribeAndPublish::callbackFilter, this);
void callbackFilter(const sensor_msgs::LaserScan& inputScan, const std_msgs::Float32& inputAngle1, const std_msgs::Float32& inputAngle2);
Would someone have an accurate idea (or, my dream, an example code :D) of how to implement that ?
Sorry if I missed the right forum post to solve my problem !
Should the three topics be synchronised (ie: use msg from time
tfrom topic 1, 2 and 3)? If so, look atmessage_filters.Not necessarily, the angles and the LaserScan variables should just be updated when new data comes in. Doing it right away, thanks.
Actually, I could just use one callback method per input attribute, to update the input attributes, and at each of these updates, call another callback method that would update the output attribute (a LaserScan) and publish it ?
If it's acceptable that none of the three callbacks can guarantee (or: you run the risk of publishing a msg in cb1 that uses old data from cb2 and cb3) that it has the 'latest' data of the other two then yes, that could work.
I'm going to try this. That being said, I'm hesitating between closing this post or waiting to see if another solution is found by me or suggested by someone else :|
I would say the canonical way to do any sort of semi-synchronised publishing based on multiple message streams is to use
message_filterswith a suitable filter setup (ie: time based or something else). That is the least 'weird' and follows standard practices. That needs msgs withHeaders though.