Question

I am very new to Ruby on Rails. I don’t know what the function of the seed.rb file is, why we use this file, and why we need to run the rake db:seed command. Can anyone give an explanation with examples?

Answer 1

Bootstrapping Data

The purpose of seed data is to bootstrap your database. For example, if you have a users table where you track users’ city and state, you may want to seed a related table with U.S. state names and abbreviations before creating the first user.

Likewise, you may also want to seed things like administrative accounts, or other data that’s necessary to run your application for the first time. As a general rule, you shouldn’t add anything to a seeds.rb file that isn’t necessary to bootstrap your database or its relations.

Related Rake Tasks

The seeds.rb file is where the seed data is stored, but you need to run the appropriate rake task to actually use the seed data. Using rake -T in your project directory shows information about following tasks:

• rake db:seed
  Load the seed data from db/seeds.rb
• rake db:setup
  Create the database, load the schema, and initialize with the seed data
• rake db:reset
  Same as rake db:setup, but drop the database first

So, you can run rake db:seed to run the seeds.rb file manually at any time. However, in most cases you will probably want to run rake db:setup or rake db:reset instead whenever you bootstrap your application.