class AllYourCode < Us

Recently a client requsted that I add a new admnistration panel to an existing Rails application. I thought to myself, “That sounds simple enough?”; welll, things are never as simple. In addition to this control panel, they wanted to use an existing MySQL database and its contents which, of course, did not follow the Rails naming conventions. Anyhow, after some research here is what I came up with.

Our first stop is in the database.yml file; the file should look something like this:

# database.yml 
development:
  adapter: mysql
  encoding: utf8
  username: root
  password: 
  database: example_development

This shouldn’t be a suprise to you. The database specified above is the default database that all of our Active Record models will use; if we want to add another connection we will need to start by speficing the connection. This connection can be another MySQL, PostgreSQL, or even an Oracle connection.

# database.yml 
development:
  adapter: mysql
  encoding: utf8
  username: root
  password: 
  database: rails_development
 
# here we specify new connection
pixel_development:
  adapter: mysql
  encoding: utf8
  username: legacy_username
  password: legacy_password
  database: legacy_database

Now that we have the connections specified, we need to move to our model; it is in here where we redirect the request to a non-standard connection. I have created a new model called “Pixel” which will interface with a database used for tracking pixels.

# app/models/pixel.rb
class Pixel < ActiveRecord::Base
end

Unless we specificy another database connection, Rails will use the default enviroments database; in this case “development”. Let’s change this by adding the following line:

# this will use our "pixel_development" database
class Pixel < ActiveRecord::Base
  establish_connection :pixel_development
end
 
 
# but let's make this more dynamic so we can use 
# develpoment, production, and test databases
class Pixel < ActiveRecord::Base
  establish_connection :pixel_#{RAILS_ENV}
end

Now we should be good to go! Any requests to the Pixel model will connect to the second database. Say the table name is set in stone and cannot be modified? No problem.

# this will use our "pixel_development" database
class Pixel < ActiveRecord::Base
  establish_connection :pixel_#{RAILS_ENV}
  set_table_name "your_table_name_here"
end

After upgrading to Snow Leopard 10.6 I’ve run into yet another quirk. I tried to log on to our VPN and the Cisco VPN client gave me me the following dialog box: “Error 51: Unable to communicate with the VPN subsystem. Please make sure that you have at least one network interface that is currently active and has an IP address and start this application again.”  Umm.

I popped over to the Cisco site and tried to see if maybe there was a 10.6 update for the client, but it turns out you have to have an account with them. After doing some more searching somebody suggested reinstalling the VPN client, so I tried it, and it works!

Cliffs: Reinstall the Cisco VPN client OR you can use Snow Leopard’s built int VPN client (more on this later)

For those of you who wanted to use thoughtbot’s paperclip plugin to manage image uploads but were having trouble watermarking said images, behold!

http://github.com/ng/paperclip-watermarking-app/tree/master

I’ve been wanting to implement an asset host for my Rails app, looking over the API I saw that Rails’ asset_host only supported a single domain. I’m running multiple domains off one Rails app, so this would have been a problem. After a little research, I came up with a solution that would work for me.

I run this as a before_filter in my Application Controller.

# for my use, @site.domain returns the user's current
# domain. you should change this to whatever method
# you use to get the domain
 
class ApplicationController < ActionController::Base
before_filter :find_asset_host
 
private
 
  def find_asset_host
    ActionController::Base.asset_host = Proc.new { |source|
        asset_hosts = %w{icarus zeus aphrodite etc etc}
 
        # disable asset host for development 
        if is_development?
          ""
        else
          "http://#{asset_hosts[rand(4)]}.#{@site.domain}"
        end
      }    
  end
 
end

Need to pass a property that isn’t associated with a model? I did. It took me a few minutes, but the solution is pretty easy.

Instead of passing the instance variable your form is using, try this.

<% form_for [:admin, @post]} do |f| %>
  <%= f.error_messages %>
 
	<p>
		<%= f.label :title %>
		<%= f.text_field :title %>
	</p>
 
	<p>
		<%= label(:skip_queue, "Skip queue") %>	
		<%= check_box("overrides", "skip_queue") %>	
	</p>
 
	<p>
		<%= f.submit "Submit" %>
	</p>
<% end %>

You’d access the property of the check box like so:

# log
Processing Admin::PostsController#create (for 127.0.0.1 at 2009-03-06 03:03:01) [POST]
  Parameters: {"commit"=>"Update", "post"=>{"title"=>"Title", "overrides"=>{"skip_queue"=>"1"}}
 
# access the property
params[:overrides][:skip_queue]

Bahhh! When you update a model that contains an empty file field in Rails 2.3 the attachment is deleted. It looks like empty file fields get passed as nil and then Paperclip gets angry.

Processing Admin::PostsController#update (for 127.0.0.1 at 2009-03-05 01:21:08) [PUT]
  Parameters: {"commit"=>"Update", "post"=>{"title"=>"Post Title", "image"=>nil}, "id"=>"124"}

There are two quick monkey patches that I’ve been using, the first, was splitting off attachments to their own method (edit_attachment)…but this quickly became a nuisance. A quicker work around is to remove the attachment field, in this case “image”, from the parameters.

 
# PUT /posts/1
# PUT /posts/1.xml
def update
  @post = Post.find(params[:id])
 
  # delete the offending parameter
  params[:post].delete(:image) if params[:post][:image].nil?
 
  respond_to do |format|
    if @post.update_attributes(params[:post])
      flash[:notice] = 'Post was successfully updated.'
      format.html { redirect_to(admin_post_url(@post)) }
    else
      format.html { render :action => "edit" }
    end
  end
end

I’ve been working on a project that requires me to watermark all my images. Here’s a script I put together using rmagick. I plan on releasing a skeleton application that will accept uploaded files and watermark them.

Ideally, I’d like to use paperclip to handle uploading, and write a processor subclass to handle watermarking…unfortunately I’m running into some issues. If anybody wants to lend a hand, I have the public repository up at: http://github.com/ng/paperclip-watermarking-app/tree

require 'RMagick'
 
# load source and watermark images
src = Magick::ImageList.new("source-image.jpg").first
watermark = Magick::Image.read("watermark-image.png").first
 
# create a new, blank image with a height that is the sum of
# the source and watermark
dst = Image.new(src.columns, src.rows+watermark.rows) { self.background_color = 'white' }
 
# place the source image on the blank image
result = dst.composite(src, Magick::NorthGravity, Magick::OverCompositeOp)
 
# place the watermark over the previous transformation
result = result.composite(watermark, Magick::SouthEastGravity, Magick::OverCompositeOp)
 
# write it out
result.write('watermarked-image.jpg')

I’ve had a few guys email me asking if I had any idea why Paperclip wasn’t saving their uploaded images. Here’s a form one of them sent me:

<% form_for(@post) do |f| %>
  <%= f.error_messages %>
 
 
    <%= f.label :title %>
    <%= f.text_field :title %>
 
 
 
    <%= f.label :description %>
    <%= f.text_area :description %>
 
 
  <%= f.file_field :image %>
 
 
    <%= f.submit "Update" %>
 
 
<% end %>

Notice anything different on this form?

<% form_for(@post, :html => { :multipart => true }) do |f| %>
  <%= f.error_messages %>
 
 
    <%= f.label :title %>
    <%= f.text_field :title %>
 
 
 
    <%= f.label :description %>
    <%= f.text_area :description %>
 
 
  <%= f.file_field :image %>
 
 
    <%= f.submit "Update" %>
 
 
<% end %>

Simple mistake, but I’ve done it a few times in the early AM and wondered WTF was going on!

:html => { :multipart => true

Recently I was porting a legacy PHP application to Rails. One of the primary tasks was to resize a bunch of images. Below you can see what one of the database rows looks like.

mysql> SELECT id, filename FROM old_posts
+----+---------------------------------------+
| id | filename                              |
+----+---------------------------------------+
|  1 | unxplained-photo-1225258423-85706.jpg |
+----+---------------------------------------+
1 row in set (0.00 sec)                                                                   
 
mysql>

You’ll see that the name of the filename is stored in the database, the problem I encountered was that often times the actual file didn’t exist even though the record remained in the database.

Rails would get angry at me when I tried to resize an non-existent file. To account for this, I did the following:

if FileTest.exists?(filename)
 # some code here to
 # resize the image
end

For more information on this handy ruby module pop into the docs.