手軽な要件のcsvを手軽に生成する

csv_creator.rb

class CSVCreator
  class_attribute :directory
  class_attribute :file_name
  class_attribute :items
  class_attribute :headers
  class_attribute :options

  class << self
    def directory(directory)
      self.directory = directory
    end

    def file_name(file_name)
      self.file_name = file_name
    end

    def items(items)
      self.items = items
    end

    def options(options)
      self.options = options
    end
  end

  def do
    raise(NotImplementedError, "You must implement #{self.class}##{__method__}")
  end

  private

  def create_csv
    CSV.open(file_path, 'w', options) do |csv|
      items.each do |item|
        csv.puts row(item)
      end
    end
  end

  def row(_item)
    raise(NotImplementedError, "You must implement #{self.class}##{__method__}")
  end

  def file_path
    File.expand_path("#{directory}/#{file_name}", Rails.root)
  end
end

example.rb

class ExampleCsvCreater < CSVCreator
  directory 'books/csv'
  file_name 'books.csv'
  items Book.stock # as ActiveRecord::Relation
  options { headers: ['title', 'author', 'asin'], row_sep: ',' }
  
  def do
    Logger.info 'start'
    create_csv
  end
  
  private
  
  def row(book)
    [book.title, book.author, asin(book.asin)]
  end
  
  def asin(asin)
    'none' if asin.nil?
    
    asin
  end
end