11.3. Writing your application

If you are starting your Rails application from scratch, you must install the Rails gem first. Then you can proceed with writing your application.

Procedure

Install the Rails gem:

$ gem install rails

Example output

Successfully installed rails-4.3.0
1 gem installed

After you install the Rails gem, create a new application with PostgreSQL as your database:
```
$ rails new rails-app --database=postgresql
```
Change into your new application directory:
```
$ cd rails-app
```
If you already have an application, make sure the pg (postgresql) gem is present in your Gemfile. If not, edit your Gemfile by adding the gem:
```
gem 'pg'
```
Generate a new Gemfile.lock with all your dependencies:
```
$ bundle install
```
In addition to using the postgresql database with the pg gem, you also must ensure that the config/database.yml is using the postgresql adapter.
Make sure you updated default section in the config/database.yml file, so it looks like this:
```
default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  host: localhost
  username: rails
  password:
```
Create your application’s development and test databases:
```
$ rake db:create
```
This creates development and test database in your PostgreSQL server.

11.3.1. Creating a welcome page

Since Rails 4 no longer serves a static public/index.html page in production, you must create a new root page.

In order to have a custom welcome page must do following steps:

Create a controller with an index action.
Create a view page for the welcome controller index action.
Create a route that serves applications root page with the created controller and view.

Rails offers a generator that completes all necessary steps for you.

Procedure

Run Rails generator:
```
$ rails generate controller welcome index
```
All the necessary files are created.
edit line 2 in config/routes.rb file as follows:
```
root 'welcome#index'
```
Run the rails server to verify the page is available:
```
$ rails server
```
You should see your page by visiting http://localhost:3000 in your browser. If you do not see the page, check the logs that are output to your server to debug.

11.3.2. Configuring application for OpenShift Container Platform

To have your application communicate with the PostgreSQL database service running in OpenShift Container Platform you must edit the default section in your config/database.yml to use environment variables, which you must define later, upon the database service creation.

Procedure

Edit the default section in your config/database.yml with pre-defined variables as follows:

Sample config/database YAML file

<% user = ENV.key?("POSTGRESQL_ADMIN_PASSWORD") ? "root" : ENV["POSTGRESQL_USER"] %>
<% password = ENV.key?("POSTGRESQL_ADMIN_PASSWORD") ? ENV["POSTGRESQL_ADMIN_PASSWORD"] : ENV["POSTGRESQL_PASSWORD"] %>
<% db_service = ENV.fetch("DATABASE_SERVICE_NAME","").upcase %>

default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see rails configuration guide
  # http://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV["POSTGRESQL_MAX_CONNECTIONS"] || 5 %>
  username: <%= user %>
  password: <%= password %>
  host: <%= ENV["#{db_service}_SERVICE_HOST"] %>
  port: <%= ENV["#{db_service}_SERVICE_PORT"] %>
  database: <%= ENV["POSTGRESQL_DATABASE"] %>

11.3.3. Storing your application in Git

Building an application in OpenShift Container Platform usually requires that the source code be stored in a git repository, so you must install git if you do not already have it.

Prerequisites

Install git.

Procedure

Make sure you are in your Rails application directory by running the ls -1 command. The output of the command should look like:
```
$ ls -1
```
Example output
```
app
bin
config
config.ru
db
Gemfile
Gemfile.lock
lib
log
public
Rakefile
README.rdoc
test
tmp
vendor
```
Run the following commands in your Rails app directory to initialize and commit your code to git:
```
$ git init
```
```
$ git add .
```
```
$ git commit -m "initial commit"
```
After your application is committed you must push it to a remote repository. GitHub account, in which you create a new repository.

Set the remote that points to your git repository:

$ git remote add origin git@github.com:<namespace/repository-name>.git

Push your application to your remote git repository.
```
$ git push
```

11.3. Writing your application

11.3.1. Creating a welcome page

11.3.2. Configuring application for OpenShift Container Platform

11.3.3. Storing your application in Git

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