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Enum in msg

asked 2011-03-15 06:14:13 -0500

Hendrik Wiese gravatar image

Hi there,

does anybody know if there's a way to put an enum type into a message? How's it done?

Thanks!

Hendrik

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answered 2011-03-15 06:28:56 -0500

kwc gravatar image

You can use constants in ROS messages:

http://www.ros.org/wiki/msg#Constants

They don't map explicitly to higher-level enum types in programming languages, but they generally let you deal with the same issues.

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Do you mean something like .. create an integer field, then create a series of constant fields to map integer values to the enumerated types?
Murph gravatar imageMurph ( 2011-03-15 06:49:21 -0500 )edit
@Murph: that's correct
kwc gravatar imagekwc ( 2011-03-15 09:48:30 -0500 )edit

I know this is a very old chain, however has this been implemented? Could I have a look?

arunavanag gravatar imagearunavanag ( 2017-04-27 01:48:45 -0500 )edit
14

answered 2013-11-29 00:10:14 -0500

lucasw gravatar image

updated 2013-11-29 00:31:14 -0500

Here is an example from joystick_drivers https://github.com/ros-drivers/joystick_drivers :

$ rosmsg show sensor_msgs/JoyFeedbackArray 
sensor_msgs/JoyFeedback[] array
uint8 TYPE_LED=0
uint8 TYPE_RUMBLE=1
uint8 TYPE_BUZZER=2
uint8 type
uint8 id
float32 intensity

There is nothing special or required about the constants TYPE_LED and TYPE_RUMBLE being capitalized or having a prefix in common with the field 'type' for which they are supposed to be the values it ought to have.

In https://github.com/ros-drivers/joystick_drivers/blob/groovy-devel/ps3joy/scripts/ps3joy_node.py the usage of the enum like fields is shown for Python:

rospy.Subscriber("joy/set_feedback",sensor_msgs.msg.JoyFeedbackArray,self.set_feedback)
...
def set_feedback(self,msg):
  for feedback in msg.array:
    if feedback.type == sensor_msgs.msg.JoyFeedback.TYPE_LED and feedback.id < 4:
      self.led_values[feedback.id] = int(round(feedback.intensity))
    elif feedback.type == sensor_msgs.msg.JoyFeedback.TYPE_RUMBLE and feedback.id < 2:
...

In C++ it would look like this:

if (msg->waveform == sensor_msgs::JoyFeedback::TYPE_RUMBLE)
...
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Asked: 2011-03-15 06:14:13 -0500

Seen: 12,719 times

Last updated: Nov 29 '13