MacRuby example of using Core Data to search for Category objects

auction_table_datasource.rb

class AuctionTableDatasource
  attr_writer :app_delegate
  attr_accessor :view
 .
 .
 .
  def set_selected_category(category_name)
    context = @app_delegate.managedObjectContext
    @current_category = Category.find_first(context, by_name:category_name)

    all = @current_category.auctions.allObjects
    @all_rows = all.collect do |row|
      # This converts the Core Data object into a hash that the rest of the data source uses to display.
      translate_row(row)
    end
    view.reloadData
  end
end

category.rb

require 'entity'

class Category < Entity
end