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Subscribe from service example

asked 2013-01-10 21:44:23 -0500

flag of Czech Republic

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Hi,

lets say that I have a service that needs some additional resources which is available via topic. Is there some example how this can be implemented?

Thanks

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answered 2013-01-11 09:04:37 -0500

flag of United States of America

58457 ●128 ●550 ●526 http://www.ros.org/

The recommended way to do this is to have a subscription to the topic which stores the latest value in a persistent location. Then you can use that value in your service callback.

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I use this approach for saving images from camera, but the topic is output from some point cloud processing, that is computationally expensive. That is why I want to subscribe when the service is called.

liborw ( 2013-01-13 20:44:24 -0500 )edit

You can connect and disconnect at the beginning and end of the sevice. But you will trade off latency for lower cpuusage.

tfoote ( 2013-03-05 09:51:04 -0500 )edit

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answered 2013-01-11 02:31:18 -0500

thebyohazard
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I'm not sure what the best practice is, but I've always used ros::topic::waitForMessage. It gets one message on the topic you specify.

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Thanks for this suggestion, I didn't know about it, but I need to synchronise multiple messages using message_filters.

liborw ( 2013-01-13 20:48:48 -0500 )edit

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Last updated: Jan 11 '13

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