CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3oncreate
choise
choise

Reputation: 25244

need to generate an object on create that contains the id

so i need to create an image that belongs to my model (string with the url of the image) in the models create method. the problem is, that this image is a QR-Code that should contain the url of the object that gets created.

but the URL (of course) is unknown in the create method because no id exists at that point for the given object.

any ideas how to solve this problem?

Upvotes: 0

Views: 116

Answers (2)

Chris Bailey
Chris Bailey

Reputation: 4136

I don't see an obvious way of doing this, beyond using a non id column within the URL (e.g. make a call to generate a UDID/GUID, and use that in the url http://mysite.com/obj/#{udid}), or saving in two stages, using the after_create callback to set the image once the record has been saved:

class MyModel < ActiveRecord::Base

  after_create :set_image

  def set_image
    if image_attribute == nil
      image_attribute = generate_a_qr_code(self)
      self.save
    end
  end

end

Upvotes: 2

Sergio Tulentsev
Sergio Tulentsev

Reputation: 230286

Use two-pass saving :-)

def create
   model = Model.new params[:model]

   if model.save
     # at this point you have an id
     model.qr = generate_qr model
     model.save

     # proceed as usual
  end
end

This is for traditional databases with auto-increment column as primary key. In some databases, keys are generated using sequences that you can query to get a new value (before saving your object). In some databases (MongoDB) keys can be generated on the client completely.

Upvotes: 0

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