class ActiveRecord::Associations::CollectionAssociation

def import(*args, &block)
  unless owner.persisted?
    raise ActiveRecord::RecordNotSaved, "You cannot call import unless the parent is saved"
  end
  options = args.last.is_a?(Hash) ? args.pop : {}
  model_klass = self.reflection.klass
  symbolized_foreign_key = self.reflection.foreign_key.to_sym
  symbolized_column_names = model_klass.column_names.map(&:to_sym)
  owner_primary_key = self.owner.class.primary_key
  owner_primary_key_value = self.owner.send(owner_primary_key)
  # assume array of model objects
  if args.last.is_a?( Array ) and args.last.first.is_a? ActiveRecord::Base
    if args.length == 2
      models = args.last
      column_names = args.first
    else
      models = args.first
      column_names = symbolized_column_names
    end
    if !symbolized_column_names.include?(symbolized_foreign_key)
      column_names << symbolized_foreign_key
    end
    models.each do |m|
      m.send "#{symbolized_foreign_key}=", owner_primary_key_value
    end
    return model_klass.import column_names, models, options
  # supports empty array
  elsif args.last.is_a?( Array ) and args.last.empty?
    return ActiveRecord::Import::Result.new([], 0, []) if args.last.empty?
  # supports 2-element array and array
  elsif args.size == 2 and args.first.is_a?( Array ) and args.last.is_a?( Array )
    column_names, array_of_attributes = args
    symbolized_column_names = column_names.map(&:to_s)
    if !symbolized_column_names.include?(symbolized_foreign_key)
      column_names << symbolized_foreign_key
      array_of_attributes.each { |attrs| attrs << owner_primary_key_value }
    else
      index = symbolized_column_names.index(symbolized_foreign_key)
      array_of_attributes.each { |attrs| attrs[index] = owner_primary_key_value }
    end
    return model_klass.import column_names, array_of_attributes, options
  else
    raise ArgumentError.new( "Invalid arguments!" )
  end
end