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What did we just do?

1. The rails generate model command created a new model named Message. In doing so, Rails created two files:

a model file in app/models/message.rb. The model represents a table in the database.
a migration file in db/migrate/. Migrations are a way to update the database.

2. Open the migration file in db/migrate/. The migration file contains a few things:

The change method tells Rails what change to make to the database. Here it uses the create_table method to create a new table in the database for storing messages.
Inside create_table, we added t.text :content. This will create a text column called content in the messages tables.
The final line t.timestamps is a Rails command that creates two more columns in the messages table called created_at and updated_at. These columns are automatically set when a message is created and updated.

3. The bundle exec rake db:migrate command updates the database with the new messages data model. With this command, we instruct the bundler to execute (exec) a rake task, in this case, migrate, on the database (db).

4. Finally the bundle exec rake db:seed command seeds the database with sample data from db/seeds.rb.

Instructions

Now that we have a model, let’s move on to the second and third parts of the request/response cycle and create a controller and a route.

Generate a controller named Messages.

In the routes file, create a route that maps the URL /messages to the Messages controller’s index action.

Then in the Messages controller (app/controllers/messages_controller.rb), add an index action:

def index 
  @messages = Message.all 
end

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