Initializing active record model using invalid parameters

I have a model that contains a country_id and region_id. The form posts back the name开发者_运维百科 of the country and region (as params[:country] and params[:region]) instead of the ids. This creates a problem when calling 'new'. Is it possible to add code to the model so that the countries and regions can be located by name? I am currently doing it in the controller, but want the code to be more reusable. Is it generally acceptable to override 'new'? This will also be called on 'update'.

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You can add accessors in the model for country and region, which can do the lookup and set the appropriate database parameter. So in this example, "country" becomes a settable virtual attribute.

class Location
  attr_accessor :country
  def country= value
    country = Country.find_by_name value
    self.country_id = country.id if country.present?
  end
end

Disclaimer: code has not been verified. Be sure to review, validate, understand, and enhance with error checking.