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Say I have 2 rostopic messages subscribers A and B listening to 2 different topics "a" and "b", however, I would to only processing the msg in A when the subscriber B got all messages from topic "b"(i.e. until there is no new message from b), is it possible to do it?
if i understand correctly you can use something like this:
void callback_b(...)
{
time = ros::Time::now().toSec();
index=0;
...
}
void callback_a(...)
{
if(ros::Time::now().toSec() - time > 3)//3 seconds that we don't have a message from b
{
//do something
}
buff[index] = *msg;
index++;
}
you can create buffer to save msg in 3 seconds some thing like the answer(i edited the answer)
some thing like time out , if no new msg arrive after 3 sec i assume there is no new msg . yes there is no guarantee that we 've received the last message but if we know the hz of msg in topic b we can use some thing like timeout
I would to only processing the msg in A when the subscriber B got all messages from topic "b"(i.e. until there is no new message from b), is it possible to do it?
No. Not with just rostopic alone.
I'm also wondering what you mean by "processing the msg": rostopic does not really process messages. It can only print them to the console, or publish new ones.
And something to consider: when are "all messages on a topic" received? How would you know?
yes, I know rostoopic doesn't really process messages. we can process the msgs from callback funciton of the rostopic. However I need the all msgs from B topic ,i.e.(until no new msg received from B topic) such that I can do sth in rostopic A's callback function
Asked: 2018-11-30 10:31:49 -0500
Seen: 350 times
Last updated: Dec 02 '18
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