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Upgrading to the latest RubyGems in Ubuntu Gutsy is a bit non-straightforward. I’d like to share a quick fix this time. It’s trivial when you know it, but if not, a friend of mine has almost hosed his system just because of this annoying “bug”.

Installing Ruby in Ubuntu is pretty simple:

sudo aptitude install ruby ri irb rdoc rubygems libruby-extras libmysql-ruby ruby1.8-dev

(add other packages as you see fit)

The problem occurs right after you upgrade RubyGems to the latest version:

sudo gem update --system

Then you get something like this:

ceefour@caliva:/usr/bin$ gem
/usr/bin/gem:23: uninitialized constant Gem::GemRunner (NameError)

Logging in and out doesn’t work. The world is coming to an end!

Don’t worry, the world is still running. Check out your /usr/bin folder:

ceefour@caliva:/usr/bin$ ls -la gem*
-rwxr-xr-x 1 root root 701 2007-08-24 12:18 gem
-rwxr-xr-x 1 root root 698 2008-03-20 09:20 gem1.8
-rwxr-xr-x 1 root root  84 2008-03-20 09:20 gemlock
-rwxr-xr-x 1 root root  89 2008-03-20 09:20 gem_mirror
-rwxr-xr-x 1 root root  76 2008-03-20 09:20 gemri
-rwxr-xr-x 1 root root  89 2008-03-20 09:20 gem_server
-rwxr-xr-x 1 root root  86 2008-03-20 09:20 gemwhich

So, there is some mismatch between gem and gem1.8. The latter being the newer/correct version.

Simply remove the “gem” one and replace (or link) it to the “gem1.8″ one:

ceefour@caliva:/usr/bin$ sudo rm gem
ceefour@caliva:/usr/bin$ sudo ln -s gem1.8 gem

Now:

ceefour@caliva:/usr/bin$ gem -v
1.0.1

Presto! We’re back in business.

Interesting RubyGems articles:

• Compiling Ruby, RubyGems and Rails on Ubuntu
• Jag har litet bråttom: Ruby Gems on Ubuntu Linux
• :: nEvEr gIVeUp :: » Ruby, RubyGems Mirroring
• VMUNIX Blues » Blog Archive » Ruby GEMS still doesn’t work on 10.4?
• Stefano’s Blog(s) » The magic world of Ruby, Rails and RubyGems …
• Ruby/RubyGems/Rails/MySQL installation h e double-hockey sticks …

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While using Ruby for your projects, you may need some references.

These are some references that might help you in using Ruby:

• Language

General Syntax Rules

• Comments start with a pound/sharp (#) character and go to EOL.
• Ruby programs are sequence of expressions.
• Each expression is delimited by semicolons(;) or newlines unless obviously incomplete (e.g. trailing ‘+’).
• Backslashes at the end of line does not terminate expression.

Reserved words

alias   and     BEGIN   begin   break   case    class   def     defined
do      else    elsif   END     end     ensure  false   for     if
in      module  next    nil     not     or      redo    rescue  retry
return  self    super   then    true    undef   unless  until   when
while   yield

Type

Basic types are numbers, strings, ranges, regexen, symbols, arrays, and hashes. Also included are files because they are used so often.

Variables

$global_variable
@@class_variable
@instance_variable
[OtherClass::]CONSTANT
local_variable

• Standard Library

Ruby comes with an extensive library of classes and modules. Some are built-in, and some are part of the standard library. You can distinguish the two by the fact that the built-in classes are in fact, built-in. There are no dot-rb files for them.

Built-in Library

Class Hierarchy:

Object

• Hash
• Symbol
• IO
  • File
• Continuation
• File::Stat
• Data
• NilClass
• Exception (see tree above)
• Array
• Proc
• String

Standard Library

The essentials:

• • benchmark.rb a simple benchmarking utility
  • cgi-lib.rb decode CGI data – simpler than cgi.rb
  • cgi.rb CGI interaction
  • date.rb date object (compatible)
  • debug.rb ruby debugger
  • delegate.rb delegate messages to other object
  • English.rb access global variables by english names
  • fileutils.rb file utility methods for copying, moving, removing, etc.

• Tools: ruby(Command Line Options, Environment Variables), irb, xmp, ruby-mode, Debugger, rdoc

• Mindshare, Idiom and Patterns (Object Design, Other Third-party Libraries)

For further details visit Ruby Quick Reference page at ZenSpider.

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Recently I got a task which involves moving, or let’s say copying, an entire Subversion repository with history to another server. Problem is, I didn’t have access to the server itself, which means I couldn’t do a regular “svnadmin dump”.

SVK comes to the rescue!

To make it work, first of all you need to install SVK. In Ubuntu it goes like this:

sudo aptitude install svk

When you first run svk it’ll ask you to create a local depot, you can simply agree to its suggestion.

Now we mirror both of the Subversion repositories we’re trying to import and export from and to. Note that you need to create the destination repository first.

svk mirror //source http://svn.source.com/project1/
svk mirror //dest http://svn.dest.com/newproject/

A bit of niceness with this method instead of a regular svn dump/load procedure is that:

• you can import to a different folder/subfolder instead of the root folder
• you can do a partial export (subfolder of project repository)

Before doing the actual migration process, let’s sync these mirrors first:

svk sync //source
svk sync //dest

And then you’ll do the real thing. But we can simulate it first by using “–check-only”, kinda’ like when you simulate a DVD burning session before actually writing it.

svk smerge //source //dest --incremental --log --sync --verbatim --track-rename --baseless --check-only

There are several switches that I used above, feel free to use them only as needed:

• -I [--incremental]: apply each change individually
• -l [--log]: use logs of merged revisions as commit message
• -B [--baseless]: use the earliest revision as the merge point
• -s [--sync]: synchronize mirrored sources before update
• –verbatim: verbatim merge log without indents and header
• –track-rename: track changes made to renamed node
• -C [--check-only]: try operation but make no changes

After you’re ready, redo the above command without “–check-only”:

svk smerge //source //dest --incremental --log --sync --verbatim --track-rename --baseless

Simply wait several minutes–or possibly hours (or days!) if your project is sufficiently large–for SVK to do its job for you!

Are there disadvantages of using SVK to a “genuine” SVN dump/load? Sure, among them is that the original author names are lost.

Good luck!

Related articles and resources:

• HomePage – SVK Wiki
• An introduction to git-svn for Subversion/SVK users and deserters
• Distributed development with SVK
• An SVK primer | Tools | New Artisans LLC
• Make it happen: Using SVK for offline access to subversion
• jkraemer.net: Work offline with SVK and Subversion
• SVK – Mirror Subversion Repositories Locally and More at sablog.com

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Ruby is a high level, object-oriented open source scripting language. It has excellent support for regular expressions as a language feature.

In Ruby, a regular expression is written in the form of /pattern/modifiers where “pattern” is the regular expression itself, and “modifiers” are a series of characters indicating various options. The “modifiers” part is optional. This syntax is borrowed from Perl.

Ruby supports the following modifiers:

• /i makes the regex match case insensitive.
• /m makes the dot match newlines. Ruby indeed uses /m, whereas Perl and many other programming languages use /s for “dot matches newlines”.
• /x tells Ruby to ignore whitespace between regex tokens.
• /o causes any #{…} substitutions in a particular regex literal to be performed just once, the first time it is evaluated. Otherwise, the substitutions will be performed every time the literal generates a Regexp object.

You can combine multiple modifiers by stringing them together as in /regex/is.

In Ruby, the caret and dollar always match before and after newlines. Ruby does not have a modifier to change this. Use \A and \Z to match at the start or the end of the string.

Since forward slashes delimit the regular expression, any forward slashes that appear in the regex need to be escaped. E.g. the regex 1/2 is written as /1\/2/ in Ruby.

Read more on: Regular-Expressions.info home page.

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Morph Labs is currently beta-testing their next-generation solution in application deployment, delivery, and management, the Morph Application Platform.

Acquiring hardware and configuring software to support web apps are things of the past. Morph Labs brings you the next-generation solution in application deployment, delivery, and management. Reduce your time to market and lower your startup costs no matter if you are an ISV, a developer or a business.

About Morph Labs

Morph Labs Inc. www.morphexchange.com is a Philippine-based Web 2.0 technology company focused on providing innovative technologies and applications to support Software as a Service (SaaS) globally.

Morph offers independent software vendors (ISVs), IT consulting organizations, application developers and entrepreneurs the quickest and simplest route to SaaS-enablement. Morph simplifies deployment and management of software as a service with an elastic Web 2.0 delivery and management solution — the Morph Application Platform.

Morph Application Platform, powered by Amazon EC2 grid computing technology, combines the elasticity in delivering and managing Web 2.0 applications and the simplicity of deploying software as a service (SaaS).

With no hardware to buy and no software to install and configure, Morph allows developers to easily grow or shrink their application environment on demand without disruption to the application. The Morph Application Platform is offered through a subscription to a Morph AppSpace, which is an instance of the Morph Application Platform.

Beyond delivery platforms and managed services, Morph will build simplified software applications (that run on our platform) that leverage open source technologies for small and medium businesses.

Morph’s first on-demand application is Morph helpME (released October 2007), provided via the software as a service model and runs on top of the Morph Application Platform. It’s an on-demand help and training system that enables sharing of knowledge while reducing overall cost and technical burden.

Morph helpME is a Ruby on Rails application running on the Morph Application Platform. It’s automatically formats, structures and creates menus, enabling faster deployment of new content.

If you are Ruby on Rails developers, bring your on-demand application to life with the Morph Application and leave the details to us!

Visit Morph home page to find out more!

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Monkeybars is a library that enables you to make use of Swing from JRuby.

Monkeybars aims to allow you to continue using the GUI editing tools you are used to but makes it easy to write all your application logic in pure Ruby. In fact, with most editors you’ll never even have to look at Java code.

Monkeybars was created from a pretty specific need. Rising Tide Software company was working on a large Swing application and wanted to be able to easily write all the logic in Ruby via JRuby. The initial attempts laid the groundwork for what was to become Monkeybars. Monkeybars has an emphasis on using normal Swing development tools (using Netbeans 6) and especially the ability to sit down with a client and use a visual designer to create the Swing layouts.

To this end, Monkeybars is designed to reach in and integrate itself with a Java class without any special consideration on the Java side. This means Monkeybars should work with Java code emitted from any Swing form designer, we don’t parse the code directly so there is no issue with code formatting or code conventions used inside the class.

Want to set up mouse event listeners on all elements in your form?

add_listener :type => :mouse

Or how about declaring that only the components okButton and cancelButton should get mouse events?

add_listener :type => :mouse, :components => ["okButton", "cancelButton"]

Testing

A second important consideration for us was testability. Our early attempts to create a Ruby interface to Swing left us with brittle, difficult to test code. Therefore in Monkeybars we implemented a stark separation between controller and view. All* communication between the two is accomplished via a model which is just a plain Ruby class. This keeps your controllers much more testable. The views also are typically smaller and much easier to test, only being concerned with their methods to convert data from and back into the model.

For further details visit: Monkeybars project page

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A common stumbling block for beginner Rails developers is learning the basics required to write plugins. This is made more complicated by the fact that Ruby is inherently dynamic and offers many techniques for code reuse.

Luckily, if you can write Rails applications you can write plugins by simply drawing on a handful of basic patterns.

Why write plugins?

Writing a plugin will:

• Help make sharing code more efficient, whether it’s between projects or within the same project
• Allow you to publish generic code to the community
• Save time and increase your confidence by testing once and reusing many times
• Share functionality in a robust manner, especially when using namespaces with ActiveRecord

Usage

Rails provides installation scripts through script/plugin install, and a generator for creating new plugins: script/generate plugin. These will work with URLs, saving time when trying out plugins. You can read more about installing and managing plugins at the Rails wiki.

Rubyisms

Any of the following tools and techniques provided by Ruby are used by plugins to extend functionality:

• Mixins: including or extending classes using modules
• Opening a class or module definition and adding or overriding methods
• Dynamic extension through callbacks and hooks: method_missing, Class#inherited, Module#const_missing, Module#included
• Dynamic extension through code generation: eval, class_eval, instance_eval

These techniques fall into two broad categories:

• Using modules and classes to extend existing classes, providing new features
• Using introspection to adapt generic code to specific cases

It’s important to consider exactly what should be extended when writing a plugin. If complex meta-programming to adapt your plugin to the host application is required, care should be taken to ensure concurrency will not produce unexpected results.

Hopefully this very short summary clears things a bit. Read more on Alex Young’s article.

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RM-Manage is a monitoring product for Rails applications. Their claim:

Building elegant and powerful Rails applications rapidly is important. Ensuring that they perform properly once deployed in production is even more important. A poorly performing or unavailable business-critical application can have a devastating impact on your bottom line, negating the benefits of Rails development.

Rails applications are more than just Rails itself. Databases like MySQL and Oracle, web servers such as Apache, and even the host operating system each affect performance and availability.

Although you may have done a great job designing a well-behaved Rails application, the fact is you won’t know how well it will truly perform until you monitor and respond to it in production. RM-Manage wraps the task of monitoring your applications in a simple and affordable interface.

Application Browser

The Application Browser for Rails allows you to view and filter important performance metrics for your production Rails applications. The application browser quickly gathers collected Model, View and Controller statistics such as averages, slowest and fastest performing models or views and more making it easy to explore application problems and bottlencks.

Screen Highlights

1. Browse and select a particular system and production Rails application for which to view performance metrics.
2. See a full list of actions in the selected application grouped by their respective controllers. Select an action to see all its related MVC information.
3. Take a closer look at the amount of time spent in the controller, model and view layers.
4. Filter method invocation information by the model, view or controller layer to see common metrics such as average, slowest and fastest invocation times, ordered by severity for the currently selected filter.

As your applications evolve and expand, you will encounter performance and availability problems. How will you troubleshoot and accurately diagnose these issues? How will you know for sure if the problem is a bug, a memory leak, a database connection issue, or a design issue? How will you ensure performance and uptime?

RM-Manage is the first and only Rails application monitoring product to instrument and monitor all aspects of the Rails framework and its supporting infrastructure resources.

RM-Manage makes it easy to design your Rails applications for optimal performance and reliability. Define personalized views of performance data (timings, counts, errors, size) based on how you want to view your application. Use the other integrated monitoring services to provide you with all the tools you’ll need to troubleshoot your application and its underlying infrastructure.

Interested? Read more at FiveRuns’ site.

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Practical Reporting with Ruby and Rails is a great book for Ruby and Rails developers seeking to create compelling business intelligence and reporting solutions using a wide variety of applications and services. Published by Apress, and the author is David Berube.

Business intelligence and real-time reporting mechanisms play a major role in any of today’s forward-looking business plans. With many of these solutions being moved to the Web, the popular Rails framework and its underlying Ruby language are playing a major role alongside web services in building the reporting solutions of tomorrow.

Practical Reporting with Ruby and Rails is the first book to comprehensively introduce this popular framework, guiding readers through a wide-ranging array of features. Note this isn’t a staid guide to generating traditional reports, but rather it shows you how the Ruby language and Rails framework can create truly compelling reporting services by plugging into popular third-party applications and services such as Google AdWords, UPS.com, iTunes, and SalesForce.com.

There’s a lot to learn from this book, including:

• Create reporting solutions for both the Web and the desktop.
• Integrate with powerful third-party retail solutions such as eBay, and Amazon.com in order to monitor your sales campaigns in real-time.
• Build an invoice reporting system using Rails and PayPal.
• Monitor your sales performance by taking advantage of SugarCRM’s web service offerings.

More resources:

• Editorial review at Amazon.com

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