Replacing 'extensions' in proto3

[R.C.]

Hi,

I am looking to move an application written with proto2 to use proto3. I understand 'extensions' is disabled in proto3 and am looking for some guidance to change the below to proto3:

========================

common.proto:

message Vehicles {

    extensions 1 to max

}

========================

car.proto:

import "common.proto";

message Car {

    string type = 1;

    string color = 2;

}

extend Vehicles {

    optional Car CarExt  = 100;

}

========================

bike.proto:

import "common.proto";

message Bike {

    string type = 1;

    string color = 2;

}

extend Vehicles {

    optional Bike BikeExt = 200;

}

========================

Since 'optional' is default i can remove the 'optional' keyword but I am not sure how 'Any' can be used in such scenario in the place of 'extensions'.

Thanks,

rc

[Bo Yang]

message Vehicles {

  Any extending = 1;

}

// cpp code ==================

Car car = new Car();

UnpackAny(vehicles.extending, &car);

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[R.C.]

Hi Bo,

Thanks for your response. Would using 'Any' in this fashion change the format on the wire? How can I edit the proto file to maintain the format on the wire (maintaining backward compatibility with older message decoders)?

Thanks,

rc

[Josh Humphries]

On Mon, Jun 5, 2017 at 4:48 PM, R.C. <karsh...@gmail.com> wrote:

Hi Bo,

Thanks for your response. Would using 'Any' in this fashion change the format on the wire? How can I edit the proto file to maintain the format on the wire (maintaining backward compatibility with older message decoders)?

Yes, using an `Any` field changes the wire representation. If you are trying to maintain binary compatibility in your move to proto3, you will have to replace extensions with actual fields with the same type and tag on the Vehicles message:

message Vehicles {

  optional Car car = 100;

  optional Bike bike = 200;

}

You would also then need to re-structure your files, like moving the definition of Vehicle into its own file, so you don't accidentally introduce any import cycles.

 

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[L Jun]

Hi, did you solve it ?  how?

[Karsh R.C.]

L Jun,

I did not change the proto format. Continuing to use proto2 :|

--rc

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