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gazebosim / gz-msgs

Messages for Gazebo robot simulation.
https://gazebosim.org
Apache License 2.0
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What is the purpose of ignition::msgs::Double_V? #152

Closed rahulbhadani closed 3 years ago

rahulbhadani commented 3 years ago

What is the best use case for ignition::msgs::Double_V?

I can see the documentation at https://ignitionrobotics.org/api/msgs/5.3/classignition_1_1msgs_1_1Double__V.html#af5fc2c48339eb12a5c2c09eeecf19ca5

but it doesn't tell me where to use this kind of message?

mjcarroll commented 3 years ago

The Double_V is currently used is to support a "tagged union" variant implementation in the Packet message: https://github.com/ignitionrobotics/ign-msgs/blob/1fe993929c815c31c7c38b3b0307782034367d9a/proto/ignition/msgs/packet.proto

This is largely an artifact of how protobuf itself works, which doesn't allow you to have a repeated field in a oneof structure, and does not allow you to repeated a oneof structure.

If you are looking to create an array of doubles in your own message, repeated double should be sufficient.

mjcarroll commented 3 years ago

In the future, I believe this type of question is better suited to Gazebo Answers