Binary Code

Pagination is one of those things that almost every site needs and for which there is absolutely no glory. Boring stuff, pagination, the Edmonton of software development. Which might explain why, when I needed to figure out how to paginate in Merb a little while ago, it was so difficult to find clear instructions on how to do so. When you find yourself in pagination you do what you have to do and then move on, with nary a glance back (apologies to both my readers in Edmonton, but you know I’m right.)

Oh sure, lots of posts on the web say “use Lori Holden’s dm-is-paginated with merb-pagination” but none say quite exactly how. And while I’m fully willing to concede I may be a little thick sometimes I found the examples on her pages somewhat under-enlightening. Hints of light bulbs but no switches, as it were.

So, embarking under the assumption that both dm-is-paginated and merb-pagination are installed on your system, here’s how I got pagination working with Merb. In this example I’ll use my DbAdminLog class as an example.

First, make sure you have the dependencies declared in dependencies.rb. At the time of this writing, these were:

dependency "merb-pagination", "0.0.1"
dependency "dm-is-paginated", "0.0.1"

In the DbAdminLog model, I added this line underneath my property definitions and validations:

is_paginated

This provides the pagination methods to the model necessary elsewhere. If you don’t add this line, no pagination for you, which is funny because it isn’t mentioned anywhere on the example pages linked above ( “…on public display in the local planning department for months, locked in a filing cabinet in the darkened cellar behind a sign that says, ‘Beware of the Leopard’”.)

In the DbAdminLogs controller I added the following to the index() method:

def index
  @current_page = ( params[:page] && ( params[:page].to_i > 0 ) ) ? params[:page].to_i : 1
  @page_count, @db_admin_logs = DbAdminLog.paginated(  rder => [ :created_at.desc ], :conditions => cond, :page => @current_page, :per_page => 20 )
  display @db_admin_logs
end

The first line figures out which page of results we’re displaying, based on the GET parameter supplied (or not supplied, in the case of the default “1″.) The second line is the pagination magic in which I define the order to be displayed (they’re log files, so LIFO), any filtering conditions via the cond variable (if you want every record unfiltered you can leave :conditions out or replace cond with ["1"]), the page number and the number of entries to be displayed per page.

(For extra credit, swap out the && with andand and be 1337.)

That’s the controller.

The view is pleasantly straightforward. In index.html.haml I added the following at the bottom below the display code:

= paginate( @current_page, @page_count, :inner_window => 5 )

And there you have it: merb pagination.

I wish I knew the original source for this quote. Anyone?

Duplicate code is the root of all evil in software design. When a system is littered with many snippets of indentical, or nearly identical code, it is indicative of sloppiness, carelessness, and sheer unprofessionalism. It is the guilt-edged responsibility of all software developers to root out and eliminate duplication whenever they find it.

From An Accidental Doppelgänger in Ruby.

Last month I started rewriting the admin reporting section of one of my sites in Merb rather than refactor the existing PHP version, for a number of reasons. The pace of development with Ruby and Merb was tremendous and within about a week and a half I had a fully-functional, extensible reporting site developed, replete with graphs and statistics. DataMapper made tying into the legacy database, with it’s rather novel table and column naming schemes, trivial. It was all tremendously satisfying and, dare I say it for a project so unglamorous, fun.

And then I tried to get it to run on our production server, which is running Red Hat Enterprise Linux 5, and the fun went away.

I first tried installing Phusion Passenger (a product I’m absolutely enthralled by) but no such luck; it had a hell of a time with the default Apache install and lack of development headers and various file locations. I wasn’t willing to muck about with the production server in a vain attempt to force it to work at the risk of the rest of the site.

Instead I figured it ought to run just fine on Rack. And every dependent gem installed with nary a hitch save for DataMapper, specifically do_mysql, which would fail to build the native extension with the following error:

In file included from /usr/include/mysql/my_global.h:83, from do_mysql_ext.c:6:
/usr/include/mysql/my_config.h:15:28: error: my_config_i386.h: No such file or directory

The solution was ultimately provided by Dan Kubb:

We probably should make it so that all the DO driver specs can be run on installed gems, but in the meantime, checkout the source from git using the following commands:

git clone git://github.com/datamapper/do.git
cd do/data_objects
sudo rake install
cd ../do_mysql
... remove the references to my_config.h in do_mysql ...
rake compile spec
sudo rake install

This will first install the edge version of DataObjects, and then will compile and run the specs for do_mysql, and then install it. You will want to remove all references to my_config.h from the do_mysql C libs just prior to running the specs of course.

The really important bit here: “remove the references to my_config.h in do_mysql”. That’s the magic, and with that everything was good and right and Merb was run, and the users were happy.

(For the very curious, the entire DataMapper Google Groups thread.)

this is an attempt to write a blog using nothing but voice recognition. The software in question is called MacSpeech Dictate which I’ve been using on and off for about the last two or three months. So far it’s extremely impressive; this post as you see it is exactly as MacSpeech Dictate has translated it without any manual corrections made by me.

So far the hardest part of using MacSpeech Dictate has been cognitive; I still find it very difficult to compose speak and read at the same time, for the process of dictation is very different in the process of type. That last sentence should read: “… very different than the process of typing.”

In a nutshell, while it’s taken me probably four or five times longer to compose this post by speaking rather than typing it is pretty cool not to touch the keyboard at all. And for someone who’s recovering from an RSI MacSpeech Dictate just might be the ticket.

(I’m very impressed that recognized RSI)

One of the projects I’m working on uses Smarty as its templating engine. Frankly in a post-Rails/Merb/CakePHP/Django world Smarty is pretty painful to work with and its age and implementation restrictions become readily apparent… but that’s another post for another time.

This post is about how spaces in Smarty templates might trip you up. Witness the following code from a Smarty template (yes, this is kind’a like PHP but less functional and less readable):

<img src="{$deletion_item->default_image(false)}" />

<img src="{$deletion_item->default_image( false )}" />

One would tend to think, or at least I tend to think, that those two lines of HTML/Smarty code would be functionally equivalent. They look the same, save for the second developer’s preference for some extra whitespace.

However example one works with Smarty, example two throws the following error:

Fatal error: Smarty error: [in /Users/chris/Sites/dreambank/templates/en/delete_item.tpl line 42]:
syntax error: unrecognized tag: $deletion_item->default_image( false ) (Smarty_Compiler.class.php, line 446) in /Users/chris/Sites/dreambank/includes/smarty/Smarty.class.php on line 1095

So, there you have it. There’s not much more to this than to say: when working with Smarty be very careful with your whitespace.

Last week Eric Kidd announced the latest version of Mephisto, the Rails-based blogging system, has been released:

Mephisto 0.8.2 is now available on the download page!

Mephisto’s JavaScript is in much better shape, and most of the remaining “tainted string” errors should now be fixed. The default article and comment filter is now Textile (instead of raw HTML), and our gem management has been cleaned up.

I mention this here, vainly, because I’m cited in the contributor notes, having fixed a couple of very minor bugs.

Mephisto still has a long, long way to go before it can lay claim to rivaling the likes of WordPress but it appears to be coming along slowly but surely ( “Don’t call me Shirley”). At the very least I can say without hesitation that the Mephisto source code is much nicer to work with that that of any other blogging platform I’ve had to dig into; in fact, compared to hacking WP, Mephisto is pure pleasure.

To check out the blog I’m running on Mephisto, take a look at Beers ‘n Booze, a blog dedicated to drinking quality beer in Vancouver.