Alex Le’s Blog

I just checked out the 280Slides.com, a YCombinator’s funded company. They are developing an online Slideshow/Powerpoint site (yes, another one). The application is pretty slick and it has the Apple’s look and feel to it (both the 2 founds were from Apple). Paul Graham used their app to create his slide at StartupSchool 2008, which at the time, took him 10 minutes to start his slides due to “technical issues”.

What really got me amazed is that they developed a JavaScript UI framework called Objective-J. Apple do a lot of their apps and gadgets in Objective-C (iPhone for one), and since the guys behind 280Slides were from Apple, probably they took the concepts from Objective C and bring it over to JavaScript. Having coded TubeCaption’s caption editor, the Captionizer, from scratch, I understand how much work it takes to do something non-trivial in JavaScript. Programming an online application is totally different than programming a simple “Ajaxy, Web2.0″ page because the amount of work involved. We have hundreds of objects potentially interact with one another and trying to compete for CPU. Without a solid foundation, the application won’t be able to bear the performance and complexity weight.

I’m pretty excited to hear that 280Slides is planning to open-source their framework (probably the Objective J) in the near future. It will be a fresh idea besides the currently established frameworks such as YUI, Ext, Prototype.

Increasingly I see the trend of JavaScript being used as the underlining cross-platform language to build other frameworks and programming languages on top of it. John Resig (from jQuery) recently ported the processing visualizing language to JavaScript. His JS implementation looks AMAZING (check out the parser’s code, what a work of art) and performance-wise the library kicks major ass. Then somebody wrote a Ruby VM in JavaScript (HotRuby) and Ruby code can get executed natively in the browser. A VM written in JavaScript? WOW! Just the thought of Rails *may* work in the browser (hopefully not IE6) makes me feel dreamy. These stuffs are truly innovative and that’s what really push the web technologies forward. And with the new JavaScript engines that promise excellent performance (Webkit’s Squirrelfish, Mozilla’s SpiderMonkey), for sure we will even see MORE of the creative innovations.

PS: don’t forget to check out www.tubecaption.com’s Captionizer, the first timeline-based caption editor.

If you do “gem install capistrano”, the gem package manager will go fetch the latest gem version of capistrano, currently 2.3.0 and installed in the gem repository. In case you want to have multiple version s of capistrano running, here’s how to do it.

To install older gem version of Capistrano
gem install –version 1.4.2 capistrano
(1.4.2 is the latest one in the 1.x branch before the release of 2.0)

To run specifically the 1.4.2 version, use
cap _1.4.2_ *your_tasks_here*

Shortcut
To reduce the typing, you can make an alias in your .bash_profile on Linux to run the 1.4.2 version as cap1 (cap 2.x.x is still running as cap) using

# add this line to .bash_profile
alias cap1=”cap _1.4.2_”

Afterwards, reload the profile with

$ source .bash_profile

Since I am on Windows, what I did was creating a batch file called “cap1.bat” and saved it within my system’s PATH environment. For simplicity’s sake, I save the cap1.bat file inside my C:\Windows\System32 folder

@echo off
cap _1.4.2_ %*

The special wildcard %* will be replaced with your command-line arguments, saving you the typing.

To read more about the Capistrano 1.4.2 version, check out Jamis’s post here.

I’ve just released ActiveFixture, an enhancement to the Rails db:fixtures:load rake task. Currently db:fixtures:load doesn’t take into account the foreign key constraints hence with any tables that have foreign keys defined, db:fixtures:load would just fail miserably. As Rails is increasingly getting more into the enterprise world, the ability to handle foreign key correctly becomes more important.

I flew to New York last weekend for the VSLive! Conference. While attending VSLive! talks during the day, my mind was mostly occupied with how to solve this foreign key issue at night. After 2 days and trying multiple ways and still unable to solve the problem, I suddenly remembered about graph (good old CS classes). I turned the problem of determining the order of loading fixtures files into a graph problem of how to traverse the graph in a certain order. Breadth-first-search doesn’t give the correct answer, Depth-first-search seems to have some potentials. When I tried Depth-first-search Post order traversal, suddenly I realized that DFS post order gives the perfect solution. What’s even more beautiful is the entire traversal algorithm was only a couple lines of Ruby code as you can see from the source.

I’ve learned quite a bit about Rails and Ruby while writing ActiveFixture. I poked around the core ActiveRecord classes and see how fixture is being handled, I then learned how to use reflection to get meta data from the ActiveRecord models, then how to write rake task and componentize everything into a plugin. In the end, I feel I like working with Ruby and Rails even more. .NET is cool but somehow, to me, Ruby is more fun to work with, except for the fact that there’s no GUI debugger. I would say I would have been able to write ActiveFixture in much less amount of time had I had a Rails/Ruby IDE with an interactive debugger.

The next time I write something for Rails, I would probably give Ruby in Steel a shot. It’s quite frustrated when you are exploring Ruby, especially when someone like me isn’t that familiar with Ruby. I love the Watch and Intermediate Window in Visual Studio simply because I can hit a breakpoint and examine the application and all the variables at that moment. Currently we don’t have anything similar for Ruby and Rails for free. Ruby in Steel seems to have potentials, but $199 is quite a barrier to entry to any ruby-rails-fan. In fact, one of the main question that my boss at work asked me about Ruby on Rails, is if Ruby has any good IDE. My company is a Microsoft shop so we use Visual Studio extensively. It’s hard to convince someone who code in Visual Studio for a living to switch to a notepad-like editor (”no Intellisense, no thanks”) and start learning Ruby on Rails. Personally I use (and pay for) e-editor, however, I do miss the intellisense and the ability to hit F5 anytime to kill that freaking bug…Okay, enough of my ranting.

Anyway, here’s the good news in short: ActiveFixture is released and ready for abused. Current version is under-tested (I haven’t written any unit tests yet) and may contain bugs. For Wars of Earth, I have about 20 tables with a whole bunch of foreign key constraints (with circular references too) so I’m quite confident that ActiveFixture will work for you.

Download:

• SVN: http://activefixture.rubyforge.org/svn/

Install:

• Copy into the RAILS_ROOT/vendors/plugins
• As always, RTFM. See README for more information. I wrote a little explanation on how ActiveFixture works so enjoy It’s a nice and elegant algorithm to solve a tricky problem.

Usage:

• Make sure you have all the required yml/yaml/csv files
• Defined all belongs_to relationships inside your models
• Run

And Support:
Please vote for ActiveFixture to get included in Rails core. I’ll have even more incentives to write even more useful Rails plugins.

keywords spam: db:fixtures:load, db:fixtures:activeload, rails foreign key constraints fixtures, fixtures loading order

{{http://alexle.net/wp-content/uploads/2007/06/rails.thumbnail.png }}Working on Wars of Earth by myself, I run into several situations when I’d like to move migration files around to get them executed in a particular order. The trick is simple: just rename the sequence of the migration files to get them to be executed in the order you want.

Besides sloppy schema design (hey, I’m trying to be agile here - fix it as you go), an example of a situation when you want to move migration files around: table A has a foreign key to table B. Migration file for A is at 005, while that of B is at 010. If you try to put in the FORIEGN KEY constraint in A migration file after the table creation, migration will fail since table B hasn’t been created yet, not until migration #010. You can add another migration file just to add the FORIEGN KEY constraint from A to B, say at #020. But then you will have fragmented migration code all over the place. For production environment, this is the only solid and proven way to perform database changes. However, during development, you have the luxury to drop and recreate the entire database from scratch, it’s just a lot more convenient and makes more sense to be able to move migration files around. Ideally, you just need to run migration for B first, then you can run migration for A, which also execute the SQL to add in the FOREIGN KEY constraint properly.

Until now, you have to it manually. Imagine if you have 20 migration files in between, from 5 to 25 (like what I have), you will probably have to renumber 20 migration files. And if your project is in SVN, it would be more time-consuming and error-prone. You can either do “svn rename”, or just rename in the shell, then deleted the previous migration files and added the newly-named ones back into the repository. But what would happen if you yawn for a second and misnumber a file at #6, so you have two 006 migration files. Oops.

Worry no more, here comes **numergrate** utility to the rescue. In short, numergrate is “to numerate migration files” (or to renumber migration files)

What you need is to drop in the numergrate script (download below) inside your Rails’ script folder and you are ready to go. With this utility, you can execute at the root of the Rails project

ruby script/numergrate 5 before 25
to (test) move 005 to position 024 instead.

or

ruby script/numergrate 10 after 2 --svn
to move 010 before 002 and also rename the files in the Subversion repository.

I also took the opportunity to integrate the utility with Subversion in case your migration files are in a repository. There’s no easy way for CVS so I didn’t implement it. However, implementing renaming mechanism for other SCM should be straight forward if you know their command line renaming tool.

I hope this comes handy for you.

==== Supported tools ====

* {{http://alexle.net/wp-content/uploads/2007/06/subversion_logo.thumbnail.jpg}} Subversion (renaming files in repository)
* {{http://alexle.net/wp-content/uploads/2007/06/utilities-terminal.png}} Shell (just like renaming manually)

==== Script ====

#!/usr/bin/env ruby
# (c) 2007 Alex Le
# www.alexle.net - nworld3d@yahoo.com
# This script is developed for www.warsofearth.com. (shameless self-promotion)
# Released under the same license as Ruby
# Disclaimer: The author is not responsible for any incorrect results from running
# the script. Use it at your own risk.
#
# USAGE:
# ------
# This script is used to re-number the migration files into the desired sequence
# In development, this comes handy as you can organize migration files into logical groups
# by running a simple command line utility instead of manually renaming the filenames.
#
# numergration = numerate migration files
#
# INSTALL
# -------
# Copy numergration into script/ folder of your Rails application.
# On linux system you may have to chmod the script to be executable (+x)
#
# HOW TO RUN
# ----------
# At your Rails application root, run:
# On Windows:
# > ruby script/numergrate before|after [mode]
# On Linux: users can just run the script without calling the ruby executable since
# there’s a #! on top, provided that you set the permission correctly. (chmod to +x)
# $ script/numergrate before|after [mode]
#
# The [mode] options are
# –test Default mode to test the result before you run
# with –shell or –svn
#
# –shell Renaming file as you would do manually in the shell
#
# –svn Integrate with Subversion by executing `svn rename` on each file
# This option alters your working copy so please be extra careful.
# (a.k.a. use it at your own risk)”
#
# Example:
# ——–
# a. Move Migration file 50 to position 3, hence shifting migration files
# from 3 to 49 to the right by 1.
# > ruby script/numergrate 50 before 3
# (the above will just execute with the –test default option)
#
# Or to actually rename the files,
# > ruby script/numergrate 50 before 3 –shell (or –svn)
#
# Or you can even run
# > ruby script/numergrate 50 after 3
# to put migration file 50 after migration file 3 (shifting migration
# file 4 to 49 to the right by 1)
#
# TODO:
# —-
# 1. Better sequence handling. Currently it’s default to 000 for the
# sequence series. However, there can be potentially a lot migration files.
# (more than 999 files). The solution is to find the max sequence and
# use that as the series template
# 2. Better SVN integration.
# a. Do some checking to see if the svn client exists before running.
# Otherwise throw an error
# 3. Better sequence checking. Currently it doesn’t check for input
# range so we can have “index out of bound” errors.
#

files.each{ |file|
if file.is_changed?
if mode == “–shell”
puts ” rename ” << "db/migrate/" << file.old_name
puts " to " << "db/migrate/" << file.new_name
cp("db/migrate/" << file.old_name, "db/migrate/" << file.new_name )
rm("db/migrate/" << file.old_name)
elsif mode.downcase == "--svn"
#puts "executing svn commmand here"
puts " svn rename " << "db/migrate/" << file.old_name
puts " to " << "db/migrate/" << file.new_name
system 'svn rename --force db/migrate/' << file.old_name << " db/migrate/" << file.new_name
elsif mode.downcase == "--test"
puts " [TEST] rename " << "db/migrate/" << file.old_name
puts " to " << "db/migrate/" << file.new_name
end
end
}


==== Download ====
* To download, please click here: [[http://alexle.net/wp-content/uploads/2007/06/numergrate.zip|numergrate]] (version 1.0, 06/17/2007)

==== Note ====
* Moving migration files around can do serious damage to your database. Please be careful. This comes extremely dangerous if you are working with other people on the same repository. Please be smart about it. Use it at your own rick.
* Comments and suggestions are very welcome.
* Support me at [[http://www.warsofearth.com|Wars of Earth]] if you can. Another shameless self-promotion.