Question

New to Rails and Ruby and trying to do things correctly.

Here are my models. Everything works fine, but I want to do things the “right” way so to speak.
I have an import process that takes a CSV and tries to either create a new record or update an existing one.

So the process is 1.) parse csv row 2.) find or create record 3.) save record

I have this working perfectly, but the code seems like it could be improved. If ParcelType wasn’t involved it would be fine, since I’m creating/retrieving a parcel FROM the Manufacturer, that foreign key is pre-populated for me. But the ParcelType isn’t. Anyway to have both Type and Manufacturer pre-populated since I’m using them both in the search?

CSV row can have multiple manufacturers per row (results in 2 almost identical rows, just with diff mfr_id) so that’s what the .each is about

manufacturer_id.split(";").each do |mfr_string|
  mfr = Manufacturer.find_by_name(mfr_string)

  # If it's a mfr we don't care about, don't put it in the db
  next if mfr.nil?

  # Unique parcel is defined by it's manufacturer, it's type, it's model number, and it's reference_number
  parcel = mfr.parcels.of_type('FR').find_or_initialize_by_model_number_and_reference_number(attributes[:model_number], attributes[:reference_number])
  parcel.assign_attributes(attributes)

  # this line in particular is a bummer. if it finds a parcel and I'm updating, this line is superfulous, only necessary when it's a new parcel
  parcel.parcel_type = ParcelType.find_by_code('FR')

  parcel.save!
end


class Parcel < ActiveRecord::Base
  belongs_to :parcel_type
  belongs_to :manufacturer

  def self.of_type(type)
    joins(:parcel_type).where(:parcel_types => {:code => type.upcase}).readonly(false) unless type.nil?
  end
end


class Manufacturer < ActiveRecord::Base
  has_many :parcels
end


class ParcelType < ActiveRecord::Base
  has_many :parcels
end

Answer 1

It sounds like the new_record? method is what you’re looking for.

new_record?() public

Returns true if this object hasn’t been saved yet — that is, a record
for the object doesn’t exist yet; otherwise, returns false.

The following will only execute if the parcel object is indeed a new record:

parcel.parcel_type = ParcelType.find_by_code('FR') if parcel.new_record?