Protobuf or more precisely Protocol Buffers is a data serialization format developer by Google and it is designed to be language-agnostic. What’s important (and what makes it a better choice than ie. JSON) is that it automatically provides validation of data, preserves order in arrays and provides pre-generated classes that do all the hard work with set of setters and getters. Magic is done by compiling .proto files with schema into language files.

When I was trying to learn more about it (to actually learn what it is and why I’d like to use it), I’ve noticed that in examples directory of protobuf project on Github the ruby example is missing, even thoughruby support is build-in into protoc compiler. So I’ve decided to fix that and a ruby example now can be found in my fork

Lessons learned here:

1. array objects are added via push method, ie:

address_book.people.push(person)

2. enum comparison is done via symbols:

phone_number.type = :MOBILE
# and not through constants, as those return enum index:
Tutorial::Person::PhoneNumber::MOBILE == 0

3. Package from .proto files becomes initial namespace, ie package tutorial will result in objects embedded in Tutorial module:

module Tutorial
  Person = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("tutorial.Person").msgclass
  Person::PhoneNumber = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("tutorial.Person.PhoneNumber").msgclass
  Person::PhoneType = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("tutorial.Person.PhoneType").enummodule
  AddressBook = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("tutorial.AddressBook").msgclass
end

4. to create protobuf mapping from source .proto file you run:

$ protoc --ruby_out=. addressbook.proto
# will result in new addressbook_pb.rb file

I still need to check out Avro, but protobuf seems to be perfect data exchange format between services / applications in different languages and developed by different teams.