Generic YAML fixture loader for Rails. Supply a db/seeds.yaml file containing fixtures with sections named for their ActiveRecord models, pluralized (e.g., Queries). Invoke with rake db:seed.

seeds.rb

# Based on http://stackoverflow.com/questions/2339021/how-can-i-load-some-activerecord-models-from-a-yaml-file-and-save-them-to-the-db/

seed_filepath = File.join( RAILS_ROOT, 'db', 'seeds.yaml' )
config = YAML::load_file( seed_filepath )

config.each { |pluralized_model_name, fixtures|
  model_class = pluralized_model_name.singularize.constantize

  # If you like leaping without looking:
  # model_class.create( fixtures )

  fixtures.each { |fixture|
    # Presumably, it's silly to try to set the Rails numeric id fields explicitly, so delete those columns from the fixture.
    fixture.delete( 'id' )
    # fixture.keys.each { |column_name|
    #   if column_name =~ /_id\Z/ then
    #     fixture.delete( column_name )
    #   end
    # }

    # See if there are any existing records that are identical to the fixture we're about to create a record from, and if not, create it.
    method_name_parts = []
    arguments = []
    fixture.each { |column_name, value|
      method_name_parts << column_name
      arguments << value
    }
    method_name = 'find_by_' << method_name_parts.join( '_and_' )

    unless model_class.__send__( method_name.intern, *arguments )
      model_class.create( fixture )
    end
  }
}