Compiling Definitions

Protocol Buffers are great because they allow you to clearly define data storage or data transfer packets. Google officially supports Java, C++, and Python for compilation and usage. Let's make it ruby aware!

Let's say you have a definitions/foo/user.proto file that defines a User message.

- definitions
  |- foo
      |- user.pb.rb

// definitions/foo/user.proto
package foo;
message User {
  optional string first_name = 1;
  optional string last_name = 2;
}

Now let's compile that definition to ruby:

$ protoc -I ./definitions --ruby_out ./lib definitions/foo/user.proto

The previous line will take whatever is defined in user.proto and output ruby classes to the ./lib directory, obeying the package directive. Your ./lib should now look like this:

- lib
  |- foo
      |- user.pb.rb

The generated file defs.pb.rb should look something like this:

# lib/foo/user.pb.rb
module Foo
  class User < ::Protobuf::Message; end

  class User
    optional ::Protobuf::Field::StringField, :first_name, 1
    optional ::Protobuf::Field::StringField, :last_name, 2
  end
end

Note: The generator will pre-define all message/enum classes empty and then re-open to apply the defined fields. This is to prevent circular field dependency issues.

The generated class is now just a plain old ruby object. You can use it however you wish. Recognize that you can also compile multiple protos at the same time, just use shell glob syntax.

$ protoc -I ./definitions --ruby_out ./lib definitions/**/*.proto

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