creating_a_migration.step

goals do

  model_diagram header: 'Topics', fields: %w(id title description)

  message "The suggestotron has a list of topics that people can vote on. We'll store our topics in the database. In this step you'll do the following:"

  goal "Create a simple *Table* in the database for topics with a title and a description"
  goal "Automatically generate the corresponding *Scaffold* in Rails (namely, the *Model*, the *View*, and the *Controller*)."

end

steps do

  step do
    option "Without Docker" do
      console "rails generate scaffold topic title:string description:text"
    end
    option "With Docker" do
      console "docker-compose run web rails generate scaffold topic title:string description:text"
    end
  end

  message <<-MARKDOWN
    * `generate scaffold` tells Rails to create everything necessary to get up and running with topics.
    * `topic` tells Rails the name of the new model.
    * `title:string` says that topics have a title, which is a "string".
    * `description:text` says that topics have a description which is a "text". A "text" is like a "string" that might be very long.
  MARKDOWN

  step do
    option "Without Docker" do
      console "rails db:migrate"
    end
    option "With Docker" do
      console "docker-compose run web rails db:migrate"
    end
  end
  message "This tells Rails to update the database to include a table for our new model."
end

explanation do
  h2 "Databases don't create tables by themselves - they need instructions."

  message <<-MARKDOWN
    One of the files the scaffold command created will be named something like
    `db/migrate/20140515115208_create_topics.rb`. The numbers in the name are
    the date and time the file was made, so yours will be named differently.

    The file contains Ruby code that describes what the table will look like.
    This is called a migration file.  It tells the database how to transform
    itself into the new configuration.

    ```ruby
    class CreateTopics < ActiveRecord::Migration
      def change
        create_table :topics do |t|
          t.string :title
          t.text :description

          t.timestamps
        end
      end
    end
    ```

    `rails db:migrate` is a task provided by the Rails framework. It uses the migration file we just created (`db/migrate/201xxxxxxxxxxx_create_topics.rb`) to change the database.
    `docker-compose run web <commands>` is a way to run commands in docker web service we specified in `docker-compose.yml` earlier.
  MARKDOWN
end

explanation do
  message <<-MARKDOWN
    Here, `rails db:migrate` is a command provided by the Rails framework. It uses the migration file we just created (`db/migrate/201xxxxxxxxxxx_create_topics.rb`) to change the database. Database migration files can be crucial to code collaboration.
    `docker-compose run web <commands>` is a way to run commands in docker web service we specified in `docker-compose.yml` earlier.
  MARKDOWN

  tip "You can run `rails -T` to see a list of all the `rails` commands your app currently responds to, along with a short description of each task."
end

next_step "CRUD_with_scaffolding"
Other Pages

creating_a_migration.step
