RailsでProtocol Buffersを使用する

RailsでProtocol Buffersを使用するのに結構ハマったのでメモ

準備

rprotocコマンドのため、インストール
gem install ruby_protobuf

railsにインストールするため、Gemfileに以下を記述する
gem 'ruby_protobuf'

Gemfileの中身をインストール
bundle install

ProtocolBuffersをRubyに変換する

key_value.proto

message KeyValue {
	required string key = 1;
	optional string value = 2;
}

以下を実行してprotoファイルをRubyのコードに変換する
rprotoc key_value.proto

すると以下のようなファイルが作られるのでapp/modelsの中に配置する

key_value.pb.rb

### Generated by rprotoc. DO NOT EDIT!
### <proto file: key_value.proto>
# message KeyValue {
#       required string key = 1;
#       optional string value = 2;
# }
require 'protobuf/message/message'
require 'protobuf/message/enum'
require 'protobuf/message/service'
require 'protobuf/message/extend'

class KeyValue < ::Protobuf::Message
  defined_in __FILE__
  required :string, :key, 1
  optional :string, :value, 2

実際に使ってみる

sample.rb

require "key_value.pb"

# Railsならこのようにクラスの初期値が可
kv1 = KeyValue.new(key: "key1", value: "val1")

# serialize
kvstr = kv1.serialize_to_string

# deserialize
kv2 = KeyValue.new.parse_from_string(kvstr)

puts kv2[:key]
# => key1

# Protocol Buffersで使えるメソッド
puts KeyValue.new.methods
# => [:value, :key, :value=, :key=, :==, :[], :[]=, :inspect, :to_hash, :to_s, :clone, :dup, :initialized?, :fields, :clear!, :has_field?, :serialize_to_string, :parse_from_string, :get_field, :get_field_by_tag, :get_field_by_name, :each_field, :parse_from, :parse_from_file, :serialize_to, :serialize_to_file, :merge_from, :to_json, :`, :to_yaml, :to_yaml_properties, :blank?, :present?, :presence, :psych_to_yaml, :as_json, :acts_like?, :to_param, :to_query, :deep_dup, :duplicable?, :in?, :presence_in, :instance_values, :instance_variable_names, :with_options, :html_safe?, :pretty_print, :pretty_print_cycle, :pretty_print_instance_variables, :pretty_print_inspect, :require_dependency, :unloadable, :require_or_load, :load_dependency, :try, :try!, :instance_of?, :kind_of?, :is_a?, :tap, :public_send, :singleton_method, :class_eval, :remove_instance_variable, :define_singleton_method, :method, :public_method, :instance_variable_set, :extend, :to_enum, :enum_for, :gem, :<=>, :===, :=~, :!~, :pretty_inspect, :eql?, :respond_to?, :freeze, :object_id, :send, :display, :byebug, :debugger, :suppress_warnings, :nil?, :hash, :class, :singleton_class, :itself, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :frozen?, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :instance_variable_get, :instance_variables, :instance_variable_defined?, :!, :!=, :__send__, :equal?, :instance_eval, :instance_exec, :__id__]