mecab.rb

#- encode: utf-8

require 'natto'

class Mecab
  def self.parse(sentence)
    mecab.parse(sentence).split(";").map {|a| a.split(":")}
  end

  def self.nouns(sentence)
    nouns = parse(sentence).keep_if {|a| a[1]=="名詞"}
    nouns.map {|a| a[0]}
  end

  def self.mecab
    @mecab ||= Natto::MeCab.new(format)
  end

  def self.format
    {
        node_format: "%m:%f[0];"
    }
  end
end

MeCab環境productionに作るの面倒なのでYahoo!形態素を使うことにした
残骸