Recaptcha on Rails

I am going to show you a basic example on how to stick ReCaptcha in your Rails application.

First of all, we are gonna need the tools,
Go ahead and register an API key at Recaptcha. Then go ahead and install the plugin/gem at Ambethia's Recaptcha on GitHub.

Once we got those installed and done, first thing first is to setup the API keys.
/config/environment.rb

# Load the rails application
require File.expand_path('../application', __FILE__)

ENV['RECAPTCHA_PUBLIC_KEY']  = '6LetRwwAAAAAAHYInUoOSj2mN_2dafLelpON4VzV'
ENV['RECAPTCHA_PRIVATE_KEY'] = '6LetRwwAAAAAAHYInUoOSj2mN_2dafLelpON4VzV'

# Initialize the rails application
RecapApp::Application.initialize!

Then we are generally gonna use Recaptcha in a form submission. Let's stick it there.
/views/posts/_form.html.erb

#Add this somewhere, note the Raw as Rails 3 automatically escapes html
<%=raw recaptcha_tags %>

Then we will have to take care of the backbone in the controller. So we want Recaptcha to kick in when a user sends a POST request or submit a post.
/controllers/posts_controller.rb

def create

@post = Post.new(params[:post])
   respond_to do |format|
     if (verify_recaptcha(:model => @post, :message => "The captcha does not match!") && @post.save)
       format.html { redirect_to(@post, :notice => 'Post was successfully created.') }
       format.xml  { render :xml => @post, :status => :created, :location => @post }
       format.js
     else
       format.html { render :action => "new" }
       format.xml  { render :xml => @post.errors, :status => :unprocessable_entity }
       format.js
     end
   end
 end

The :message option will deal with the error message in the form if the captcha doesn't match.

And there you have it!