How to pass arrays in custom messages

asked 2011-09-02 09:29:54 -0500

Gideon
239 ●7 ●13 ●17

updated 2011-09-05 03:19:32 -0500

joq
25443 ●181 ●256 ●408

Hello all, I have a node publishing temperature data from a string of 8 batteries written in python. Each battery has 8 temperature sensors, and so rather than building a message with 64 fields I have it broken down into 8 arrays each of length 8. I have written a healthMap node in C++ and I want to subscribe to the temperature data. What should my message structure look like? Python wants to use a tuple and C++ wants a vector. Does anyone have a code example that illustrates how to approach this? I also have little experience working with vectors in C++, so hopefully you could give me a sketch of what the subscriber looks like as well. Sorry for the long-winded question

Cheers

Gideon

answered 2011-09-02 09:53:50 -0500

Thomas D

4347 ●33 ●65 ●86 http://denewiler.us/cv

updated 2011-09-02 10:04:38 -0500

This is similar to a previous question. There is a good answer there that has some example code and points to this tutorial. The tutorial has example code for publishers and subscribers.

For C++ vectors you can do something like the following (someone correct my C++ if I'm wrong please):

std::vector<double>::iterator my_iterator;
int i = 0;
for (my_iterator = msg.vector_field.begin(); msg.vector_field.end(); my_iterator++)
{
    my_local_battery_value[i] = msg.vector_field[my_iterator];
    i++;
}

or follow this page.

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Comments

Thanks. If my subscriber in written in C++, do I manually copy all of the fields to my local variables with a for loop?

Gideon ( 2011-09-02 10:06:19 -0500 )edit

so something like this wouldnt work?

Gideon ( 2011-09-02 10:16:38 -0500 )edit

Would this work? for(int i = 0; i<numTemps;i++){ temp[i] = msg->temp[i]; }

Gideon ( 2011-09-02 10:18:28 -0500 )edit

Well, you can also just copy the whole vector, no need for a for loop. Or ideally subscribe a shared pointer, that you store, then no copying is needed at all.

dornhege ( 2011-09-02 10:25:33 -0500 )edit

It should definitely be possible. It might even be easier than my little example code (I just haven't worked with vectors that much either).