ProtoRecord

ProtoRecord provides a simple way to build Protocol buffer messages from ActiveRecord objects based on the stubs generated by protocol buffer compiler.

Add this line to your application's Gemfile:

gem 'proto_record'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install proto_record

To make use of ProtoRecord you need have some messages defined in a .proto file and the stubs generated using using the protocol buffer compiler, for more information follow the gRPC Ruby basic tutorial.

For our exmpale we will use the following message:

message PathMessage {
  string name = 1;
  string description = 2;
}

With the stubs generated all you have to do is to include the ProtoRecord module and define a proto_message for your ActiveRecord object.

class Path < ActiveRecord::Base
  include ProtoRecord

  # 'PathMessage' will be used when resolving the object.
  proto_message :path_message
end

After including the module and defining a mesasge, a to_proto method would be added to instances of Path. Calling to_proto will return a message of type PathMessage that is built from the instance using only the fields defined on the message. A very simple scenario would be getting getting all Paths from the DB and returning them as messages. This would look something like:

Path.all.map(&:to_proto)

ProtoRecord also resolves nested messages, so if we have the following schema:

message PathMessage {
  string name = 1;
  string description = 2;
  repeated FeatureMessage features = 3;
}

message FeatureMessage {
  string name = 1;
}

And relation defined like this:

class Path < ActiveRecord::Base
  include ProtoRecord

  proto_message :path_message

  has_many :features
end

class Feature < ActiveRecord::Base
  include ProtoRecord

  # 'FeatureMessage' will be used when resolving the object.
  proto_message :feature_message

  belongs_to :path
end

Then invocking to_proto on an instance of Path will also create messages for all associated features.

ProtoRecord will also handle the creation messages for non ActiveRecord objects that define a proto_message. The only differene is that you would need define a fields_resolver that will point to a method that returns a hash representation of the class which will be used to instantiate the message. So with a message like this:

message PointMessage {
  int32 x = 1;
  int32 y = 2;
}

And class that implements Point:

class Point
  include ProtoRecord

  # 'PointMessage' will be created with the hash returned form the `:to_h` method.
  proto_message :point_message, :fields_resolver => :to_h

  def initialize(x: nil, y: nil)
    @x = x
    @y = y
  end

  def to_h
    {
      x: @x,
      y: @y
    }
  end
end

In cases when you don't want to define a message for class (e.g the class just represents a repeated message), you can simply define a to_proto method which will be invoked when creating the message.

class Points
  attr_reader :points

  def initialize(points: [])
    @points = points
  end

  def to_proto
    @points.map(&:to_proto)
  end
end

• Notice that you don't need to include ProtoRecord or define a proto_message in cases like this.

Protocol Buffer messages don't support sending dates, ProtoRecord will transform all types of dates into Time by calling to_time on them. In your .proto file you will need to add the following:

import "google/protobuf/timestamp.proto";

message ObjectWithDateMessage {
  google.protobuf.Timestamp created_at = 1;
}

• Support custom field transformation.
• Add a from_proto for creating and updating records.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/proto_record. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the ProtoRecord project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.