If you haven't yet deployed this application to heroku, start at First-time setup. Otherwise, start at Every time.

First-time setup for each application

Step 1: Create a heroku application

Type this in the terminal:

heroku create

heroku create registers a new application on heroku's system. You should see some output including your new app's URL.

Step 2: Edit the Gemfile

Each application has its own Gemfile. Be sure you're opening the one inside your app's folder.

Heroku will run our application slightly differently than our development computer does, which requires us to make a small change to our Gemfile.

Open the file called Gemfile in Sublime Text, or your preferred editor, and find the line containing:

gem 'sqlite3'

Remove that line and replace it with:

group :development, :test do
  gem 'sqlite3'
end
group :production do
  gem 'pg'
  gem 'rails_12factor'
end

Step 3: Apply the Gemfile changes

Type this in the terminal:

bundle install --without production

Every time the Gemfile changes, you need to run bundle install for the changes to be processed. The processed version of the changes is stored in another file called Gemfile.lock.

Step 4: Commit the Gemfile changes

There are now changes to Gemfile and Gemfile.lock that need to be committed before we can push to heroku.

Type this in the terminal:

git add -A
git commit -m "Changed Gemfile for heroku"

Every time

Step 1: Commit any pending changes to git

Heroku will only receive the files we've committed into our local git repository. So we need to make sure all changed files have been committed.

Type this in the terminal:

git status

git status shows you any pending changes you've created. If it has no output, you're already ready to deploy! Otherwise...

Type this in the terminal:

git add -A
git commit -m "Some helpful message for your future self"

Your commit message should reference whatever your outstanding changes are: something like 'added votes to the topics index'.

Step 2: Push changes to heroku

Type this in the terminal:

git push heroku master

This takes all changes you've committed locally and pushes them to heroku.

Step 3: Run database migrations on Heroku

Type this in the terminal:

heroku run rake db:migrate

This tells Heroku to run your migrations on its database, like running rake db:migrate locally. Heroku's database is separate from the one on your computer, which means it needs to be updated every time you make changes to the structure of your database. It also means that you'll not see any of the data you entered into the sqlite3 database on your computer.

Step 4: Visit your application

Type this in the terminal:

heroku open

This opens the new application in your browser.