Sinatra doesn't come with database support out of the box, but it's relatively easy to configure. In general, we'll be working from templates that have this pre-built, but it's good to understand what's going on under the hood. We're going to practice adding a database to our Sinatra applications.
Fork and clone this repository to get started! We have a basic sinatra application stubbed out with an
app.rb file acting as the controller.
First, we'll add three gems to allow us to use ActiveRecord:
activerecord gives us access to the magical database mapping and association powers.
rake, short for "ruby make", is a package that lets us quickly create files and folders, and automate tasks such as database creation, and
sinatra-activerecord gives us access to some awesome Rake tasks. Make sure those three gems are in your Gemfile:
gem 'sinatra' gem 'activerecord', '4.2.5' gem 'sinatra-activerecord' gem 'rake' gem 'thin' gem 'require_all'
Into our development group, we'll add two other gems:
sqlite3 is our database adapter gem - it's what allows our Ruby application to communicate with a SQL database.
tux will give us an interactive console that pre-loads our database and ActiveRecord relationships for us. Since we won't use either of these in production, we put them in our
:development group - this way, they won't get installed on our server when we deploy our application.
gem 'sinatra' gem 'activerecord', '4.2.5' gem 'sinatra-activerecord' gem 'thin' gem 'require_all' group :development do gem 'shotgun' gem 'pry' gem 'tux' gem 'sqlite3' end
Our Gemfile is up to date - awesome! Go ahead and run
bundle install to get your system up to speed.
We now have access to all of the gems that we need, but we still need to set up a connection to our database. Add the following block of code to your
environment.rb file (underneath
configure :development do set :database, 'sqlite3:db/database.db' end
This sets up a connection to a sqlite3 database named "database.db", located in a folder called "db." If we wanted our
.db file to be called
dogs.db, we could simply change the name of this file:
configure :development do set :database, 'sqlite3:db/dogs.db' end
But for now,
database.db is a great name. Notice that this didn't actually create those files or folders yet - that's how Rake will help us.
As we mentioned,
rake gives us the ability to quickly make files and set up automated tasks. We define these in a file called
Rakefile. First, create a
Rakefile in the root of our project directory. In the
Rakefile, we'll require our
config/environment.rb file to load up our environment, as well as
"sinatra/activerecord/rake" to get Rake tasks from the
require './config/environment' require 'sinatra/activerecord/rake'
In the terminal, type
rake -T to view all of the available rake tasks. You should see the following output:
rake db:create # Creates the database from DATABASE_URL or config/database.yml for... rake db:create_migration # Create a migration (parameters: NAME, VERSION) rake db:drop # Drops the database from DATABASE_URL or config/database.yml for t... rake db:fixtures:load # Load fixtures into the current environment's database rake db:migrate # Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog) rake db:migrate:status # Display status of migrations rake db:rollback # Rolls the schema back to the previous version (specify steps w/ S... rake db:schema:cache:clear # Clear a db/schema_cache.dump file rake db:schema:cache:dump # Create a db/schema_cache.dump file rake db:schema:dump # Create a db/schema.rb file that is portable against any DB suppor... rake db:schema:load # Load a schema.rb file into the database rake db:seed # Load the seed data from db/seeds.rb rake db:setup # Create the database, load the schema, and initialize with the see... rake db:structure:dump # Dump the database structure to db/structure.sql rake db:structure:load # Recreate the databases from the structure.sql file rake db:version # Retrieves the current schema version number
Let's test out our handiwork by creating a
dogs table with two columns:
breed. First, let's create our migration:
rake db:create_migration NAME=create_dogs
You should see the following output:
The beginning of the file is a timestamp - yours should reflect the time that your
create_dogs file was created! You've now created your first database migration inside of the
Inside of the migration file, remove the default
change method (we'll come back to this), and add methods for
class CreateDogs < ActiveRecord::Migration def up end def down end end
up method should create our table with
breed columns. Our down method should drop the table.
class CreateDogs < ActiveRecord::Migration def up create_table :dogs do |t| t.string :name t.string :breed end end def down drop_table :dogs end end
Now, run the migration from the terminal with
rake db:migrate SINATRA_ENV=development
SINATRA_ENV=development, you might ask? Well, remember the top line of
config/environment.rb? It's telling Sinatra that it should use the "development" environment for both
shotgun and the testing suite. Therefore, we want to make sure our migrations run on the same environment as well, and specifying
SINATRA_ENV=development allows us to do that.
You should see the following output:
== 20150914201353 CreateDogs: migrating ======================================= -- create_table(:dogs) -> 0.0019s == 20150914201353 CreateDogs: migrated (0.0020s) ==============================
The change method is actually a shorter way of writing
down methods. We can refactor our migration to look like this:
class CreateDogs < ActiveRecord::Migration def change create_table :dogs do |t| t.string :name t.string :breed end end end
While the rollback (
down) method is not included, it's implicit in the change method. Rolling back the database would work in exactly the same way as using the
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