How can I load some ActiveRecord models from a YAML file and save them to the DB?

Question

I'm trying to save some lookup table data out to a YAML file so that later when I need to set up my app on a different machine I can load the data in as seed data.

The data is stuff like select options, and it's pretty much set, so no worries about the live data changing between serializing and deserializing.

I have output the data like this...

file = File.open("#{RAILS_ROOT}/lib/tasks/questions/questions.yml", 'w')
questions = Question.find(:all, :order => 'order_position')
file << YAML::dump(questions)
file.close()

And I can load the file like this...

questions = YAML.load_file('lib/tasks/questions/questions.yml')

However, when I try to save a question I get this error...

>> questions[0].save
NoMethodError: undefined method `save' for #<YAML::Object:0x2226b84>

What is the correct way to do this?

Answer 1

Create a seed.yml file in db directory. Add a YAML document for each model you want to create. This document should contain a list of hash. Each hash should contain model attributes.

  users:
      -   login: jake
          password: jake123
          password_confirmation: jake123
          first_name: Jake
          last_name: Driver

      -   login: Jane
          password: jane123
          password_confirmation: jane123
          first_name: Jane
          last_name: McCain

  categories:

  products:

In your seed.rb file

seed_file = File.join(Rails.root, 'db', 'seed.yml')
config = YAML::load_file(seed_file)
User.create(config["users"])
Category.create(config["categories"])
Product.create(config["products"])

Run the rake task to load the rows

rake db:seed

Answer 2

Does the accepted answer actually answer the question? It looks like the asker wanted to save the models, not just retrieve them from a YAML file.

To actually save the loaded model(s) back to the database you need to fool ActiveRecord into thinking the model needs saving. You can do it with this rather dirty bit of code

questions = YAML.load_file("#{RAILS_ROOT}/lib/tasks/questions/questions.yml")
questions.each{|q| q.instance_variable_set("@new_record", true); q.save}

It works and saved my bacon once or twice.