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1. Senior Rails application developer
2. Web application developer

DRY Up Your SWF SEO

We've talked about search engine optimization with Flash before, and for large database-driven sites the methodology still applies. But for smaller Flash sites that still have great content there may be a simpler, DRYer (Don't Repeat Yourself) solution.

This technique, just like unobtrusive javascript, works best when the page is first designed for the lowest common denominator (in this case search bots or folks without Flash) and then progrssively enhanced with a richer experience when supported. With that in mind, let's start with the navigation.

<div id="nav">
<ul>
<li><a href="/" class="selected">Home</a></li>
<li><a href="/about/">About Us</a></li>
<li><a href="/contact/">Contact Us</a></li>
</ul>
</div>

Next, our page needs some content. It may have images, paragraphs, bulleted lists and some formatting. It's not XML, so we'll want to keep the tags that lend the formatting.

<div id="content">
<p>Hello <b>World</b></p>
</div>

This basic HTML has created a great foundation for our site. Screen readers, search engines, and iPhone users will all be able to enjoy our content. But for folks with Flash, we can make the experience even better. If we place the nav and content divs inside a wrapper div, SWFObject can replace the contents of the wrapper with our nifty Flash movie.

Getting started, that unordered list nav looks very familiar as HTML, but it also looks like something else — XML. So why don't we load this XML into our Flash movie? It even tells us which page we're on (via class="selected"). That will allow great flexibility with the design of the nav in Flash. Using SWFObject, it's as simple as this:

so.addVariable("xml_input", escape(document.getElementById("nav").innerHTML));

Now we should feed the content into Flash the same way as the faux XML nav:

so.addVariable("html_input", escape(document.getElementById("content").innerHTML));

All that's left is to parse the XML for the nav and render the HTML from the content. Executions will vary, but this should get us started:

// Parse the xml content
XML.prototype.ignoreWhite = true;
var myXML:XML = new XML();
myXML.parseXML(_level0.xml_input);
var rootNode:XMLNode = myXML.firstChild;
...
// Set the html content
_root.content_txt.htmlText = _level0.html_input;

This method allows the developer to spend more time building a sound, accessible site and less time creating XML schemas to load in duplicate content for two presentations. Flash supports a good subset of HTML tags as well as custom CSS, so you should be able to match most of the usual content formatting.

Bobby Uhlenbrock, Application Developer, Barefoot

NetBeans Ruby Debugger Doesn't Like Symbolic Links

Let me say that the new NetBeans 6 IDE, released in its final version just yesterday, is an amazing Ruby on Rails development environment. I love the intellisense features, quick-switching between controller, view, and test files, and so many other things. But the biggest thing I was looking forward to was the integrated debugger.

Unfortunately, on my Mac OSX Tiger system I couldn't get breakpoints to work. NetBeans just ignored them. I spent several hours trying to debug it, unfortunately led astray by a red herring. Since I'm using Rails 2.0 RC2 on my current project, and a new empty app based on Rails 1.2.5 worked great in the NetBeans debugger, I though it must be some problem in Rails 2.0. However, after eliminating everything different between the two apps, I found the real culprit.

I keep all of my production working directories in a main directory, and have a symbolic link in my home directory to provide quick access. Unfortunately, when the NetBeans project includes a symbolic link, breakpoints in the debugger don't fire. When I changed my reference to use the absolute path (sans symlink), the breakpoints work great.

Now NetBeans and I are getting along great. I highly recommend it for any Ruby or Java development.

Doug Smith, Senior Developer, Barefoot

Processing Remote Files with Attachment Fu

I've used Rick Olson's attachment_fu on a few projects now, and it's become one of the first plugins I import into my rails directory. But for my current task I need to not only upload photos but also import external images from a data service and run them through the usual cropping and scaling. I think it is ideal for all images, regardless of source, to be run through the same model where they are subjected to the same operations and validations. So that's what we'll do.

Currently, when you post a multi-part form with a file input box named uploaded_data, attachment_fu will grab that TempFile with a setter of the same name and do its magic. I have followed the same process with a new method. It can go right in the model that has_attachment:

    # Takes input of a remote file via an absolute URL,
    # reads it and passes it to attachment_fu for processing   
    def remote_data=(file_url)
      return nil if file_url.nil?  
      open(file_url) do |data|
        # extract the filename and extension from the url
        temp_filename = URI.split(file_url)[5][/[^\/]+\Z/]
        # pass details to attachment_fu
        self.filename     = temp_filename
        self.temp_data    = data.read
        self.content_type = data.content_type           
      end    
    end

This opens the attachment and places the contents in a TempFile just as if it had been uploaded. Keep in mind that while my input data is quite reliable, you may need to add a few checks to ensure you have a valid extension and mime type. You can use the new method thusly:

    photo = Photo.new
    photo.remote_data = "http://www.somewhere.com/an_image.jpg"
    photo.save

Bobby Uhlenbrock, Application Developer, Barefoot

A Fix for a WordPress Paging Problem

I recently discovered a problem in the next/previous paging links of a custom WordPress 2.2.1 site we created for Fractional Jets Focus. When viewing a list of articles by category, the previous posts link generated a 404 error.

After digging for too long through WordPress code and Google search results, I found that the problem was related to an apparent bug or conflict between the paging feature and custom permalinks.

Our custom permalink setting in Options -> Permalinks is this:

/%category%/%year%/%monthnum%/%postname%/

When you want to view all the posts for a certain category, an example URL is /blog/2007/9/. The problem is that the URL generated by next_posts_link() was misinterpreted by WordPress because of the permalink. The link was: /blog/2007/9/page/2/. Unfortunately, the string "page" in this URL was interpreted as a post name, instead of a token for the page index.

There is probably some voodoo I could have done in the .htaccess file with mod_rewrite to fix the issue, but I feared breaking something else. So, I wrote the following plugin. It's so short that I'm publishing the whole thing inline.

<?php
/*
Plugin Name: Fix Paging in Category Listings 
Plugin URI: http://www.thinkbarefoot.com
Description: Fixes a bug where next/previous links are broken in category by year/month listings
Version: 0.5
Author: Doug Smith
Author URI: http://www.thinkbarefoot.com

Copyright 2007  Doug Smith  (email: dsmith@thinkbarefoot.com)

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

*/

/**
 * Function to fix problem where next/previous buttons are broken on list
 * of posts in a category when the custom permalink string is:
 * /%category%/%year%/%monthnum%/%postname%/ 
 * The problem is that with a url like this:
 * 
 * /category/2007/10/page/2
 * 
 * the 'page' looks like a post name, not the keyword "page"
 */
function remove_page_from_query_string($query_string)
{ 
    if ($query_string['name'] == 'page' && isset($query_string['page'])) {
        unset($query_string['name']);
        // 'page' in the query_string looks like '/2', so split it out
        list($delim, $page_index) = split('/', $query_string['page']);
        $query_string['paged'] = $page_index;
    }      
    return $query_string;
}

add_filter('request', 'remove_page_from_query_string');

?>

This plugin simply checks to see whether the post name is 'page', and if there is a 'page' parameter too. If so, it removes the 'name', and assigns the page index to the magic 'paged' parameter. Paging restored.

Doug Smith, Senior Developer, Barefoot

I'm Glad Rails Loves SQL

It's a good thing that the core team for Ruby on Rails has chosen to embrace SQL, and easily expose it to developers. Other object-relational mapping layers often try to hide SQL as 'evil'. However, there are times when nothing will substitute for being able to talk directly to the database, in its own language.

Yesterday was such a time. I have an application that displays articles divided into hierarchies of categories. Articles are rendered differently on the site depending on their category.

I needed to change a list of articles from one top-level category (let's call it food) so that some articles in one of its sub-categories (call it expert reviews) only appeared one time per sub-category. So, while articles from other sub-categories of food would all appear in the list, only the latest article from any expert reviewer would appear in that same list.

I wanted to handle this in the model using a custom finder so that controllers could just call something like Category.published_article_list(options) and the details would be irrelevant.

Ok, enough background, here's the method I added to the Category model:

def published_article_list(options = {})
 if (food?)
   # Special query that returns only the latest article for each 'reviewer' category
   sql  = "mid_category_id != #{REVIEW_CAT} OR articles.id IN ( "
   sql += "SELECT SUBSTRING( MAX( CONCAT( published_on, id ) ), 11 ) AS ra_id "
   sql += "FROM articles "
   sql += "WHERE mid_category_id = #{REVIEW_CAT} AND "
   sql += "      #{Article.conditions_published} "
   sql += "GROUP BY category_id ) ) "
   options[:conditions] = sql
 end
 self.published_root_articles.find(:all, options)
end

That SQL is a little serious, so here's what it does in English. It starts by removing any articles that have a mid-level category of "review". It then adds the articles from that category that we want using a subquery.

The meat of the subquery is in this part of the SELECT clause: SUBSTRING( MAX( CONCAT( published_on, id ) ), 11 ) AS ra_id. I needed to get the ID of the latest article, grouped by category_id (the individual reviewer). So, this code concatenates the published_on date to the article ID, finds the max of all those values, then uses SUBSTRING to chop the concatenated date off, leaving only the id of the latest article. So, for a list of articles with IDs and dates like this:

id    date         category_id
101   2007-10-01   1
102   2007-09-30   1
103   2007-10-02   2
104   2007-10-01   2

When the concatenated dates and IDs are sorted, they end up like this:

2007-10-02103
2007-10-01104
2007-10-01101
2007-09-30102

Using this method, the subquery accurately adds the IDs of articles 101 and 103 to the IN clause above.

The only downside to this method is that the CONCAT function requires a full table scan, so indexes won't be used in the subquery. Since this page is cached, it wasn't a problem for this application, but if performance becomes an issue other optimization could be done while still using this strategy.

Thanks for loving SQL, Rails!

Doug Smith, Senior Developer, Barefoot

classic_pagination is not my friend

I recently upgraded a nearly completed Ruby on Rails project to version 1.2.4, then to version 1.2.5. I worked through the deprecation warnings and everything seemed good to go.

Then, I ran into a snag with pagination -- something I didn't have covered in my functional tests. Because I'm caching this site, I have routes that include the :page property for the paginator in the URL. Otherwise, pages 2-n don't get cached.

After installing the classic_pagination plugin, I'd get an error when viewing pages with pagination code like this in the view:

<%= link_to('« Previous', :page => @article_pages.current.previous) if @article_pages.current.previous %>
<%= link_to('Next »', :page => @article_pages.current.next) if @article_pages.current.next %>

This is the standard, recommended method for creating the Next and Previous links. The error said: undefined method `paginator' for "2":String. The top-most offending line of the stack trace was: vendor/plugins/classic_pagination/lib/pagination.rb:307:in `=='.

The confusing part was that when I removed the :page from the route and added ?page=2 back as a query string parameter, the error went away. In theory, the :page should be the :page whether it is on the query string or embedded in the URL, right?

Well, long story short, here's the fix. Unfortunately, I can't explain exactly why this is necessary, and don't have the time now to dig into the innards of classic_pagination and the supporting Rails infrastructure to find out. I just hope this post helps somebody.

Oh, the fix? Add the "number" method to the previous or next Page object reference, like so:

<%= link_to('« Previous', :page => @article_pages.current.previous.number) if @article_pages.current.previous %>
<%= link_to('Next »', :page => @article_pages.current.next.number) if @article_pages.current.next %>

I'll probably consider classic_pagination my friend again once I get over being grumpy about this ... or, I may consider one of the other pagination contenders for a future application.

Doug Smith, Senior Developer, Barefoot