Define dictionary in protocol buffer

Question

I\'m new to both protocol buffers and C++, so this may be a basic question, but I haven\'t had any luck finding answers. Basically, I want the functionality of a dictionary

Answer 1

In proto3, it's:

extend google.protobuf.EnumValueOptions {
  string name = 12345;
}

enum UnitType {
  KM_PER_HOUR = 0 [(name) = "km/h"];
  MI_PER_HOUR = 1 [(name) = "mph"];
}

and to access it in Java:

UnitType.KM_PER_HOUR.getValueDescriptor().getOptions().getExtension(MyOuterClass.name);

Answer 2

You could use custom options to associate a string with each enum member: https://developers.google.com/protocol-buffers/docs/proto#options

It would look like this in the .proto:

extend google.protobuf.FieldOptions {
  optional string name = 12345;
}

enum UnitType {
    KmPerHour = 1 [(name) = "km/h"];
    MiPerHour = 2 [(name) = "mph"];
}

Beware, though, that some third-party protobuf libraries don't understand these options.