When importing a CSV, how do I handle data in a ro

I am following the Import CSV Railscast and it is straight forward.

The issue is that it deals with just a csv file containing only information in 1 model in 1 file.

Say, I have a CSV file that I am trying to import to my Listing model. On each row/listing it has a column called Building where the value is actually the name of the building attribute of that listing (i.e. @listing.building.name).

How do I handle those cases in the import?

This is the closet that Ryan gets in that Railscast, which is on the Product model in his case:

def self.import(file)
  CSV.foreach(file.path, headers: true) do |row|
    product = find_by_id(row["id"]) || new
    product.attributes = row.to_hash.slice(*accessible_attributes)
    product.save!
  end
end

All that is happening is that he is checking to see if the product exists and if it does then update the attributes. If it doesn't, then create a new one.

Not quite sure how to handle the associations in this case...especially given that what needs to happen is in the event that an associated record doesn't exist, it needs to be created during this process.

So going back to my building.name example earlier, if there is no Building.find_by_name(name), then it should create a new building record.

Thoughts?

try this

def self.import(file)
  CSV.foreach(file.path, headers: true) do |row|
    product = find_by_id(row["id"]) || new
    product.attributes = row.to_hash.slice(*accessible_attributes)
    product.save!

    building = product.buildings.find_by_name(row['building_name'])
    building ||= product.buildings.build
    building.attributes = row.to_hash.slice(*build_accessible_attributes)
    building.save!
  end
end

UPDATE: updated answers using new rails 3 methods

def self.import(file)
  CSV.foreach(file.path, headers: true) do |row|
    product = where(id: row["id"])
      .first_or_create!(row.to_hash.slice(*accessible_attributes))

    product.buildings.where(name: row['building_name'])
      .first_or_create!(row.to_hash.slice(*building_accessible_attributes))
  end
end