Rails Magazine - Issue 3

6
Create a simple code snippet app with Rails by Michelangelo Altamore
6
Time to move on the next one.
Task 2: Snippet Highlighting
For this task we will use the library CodeRay by Kornelius
Kalnbach. Check if it is already installed on your system with
gem list coderay. If it is not listed you can install by running:
$ sudo gem install coderay.
Our aim is to let Snippety being able to use the coderay
gem to render an highlighted version of a snippet body according
to its language syntax.
So we configure that dependency in config/environment.rb by
adding the line:
config.gem "coderay"
We still don’t know how to interact with that library. However
that knowledge is not that far away, by running ri CodeRay
you can see its usage; I report here what is relevant for us:
Highlight Ruby code in a string as html
require ‘coderay’
print CodeRay.scan(‘puts “Hello, world!”’, :ruby).html
# prints something like this:
puts "Hello, world!"
Highlight C code from a file in a html div
require ‘coderay’
print CodeRay.scan(File.read(‘ruby.h’), :c).div
print CodeRay.scan_file(‘ruby.h’).html.div
You can include this div in your page. The used CSS
styles can be
printed with
% coderay_stylesheet
...
A bridge too red
The documentation tells us that:
1. we can obtain coderay’s stylesheet with the command
coderay_stylesheet
2. we can highlight a string calling scan method on the
CodeRay class
In order to integrate coderay stylesheet we run the following
inside root folder of Snippety:
$ coderay_stylesheet > public/stylesheets/coderay.css
You should obtain the stylesheet file. To get it loaded we
must modify application layout, as you can see on line 6 in
app/views/layouts/application.html.erb file:
...
4
5
6
7
8
...
The stylesheet should be loaded now (you can look at the
source to be sure).
Now it’s time to explore CodeRay from the Rails console:
$ script/console
Loading development environment (Rails 2.2.2)