Time for Some Fun

If you are following the Ruby mailing list, you will see we just made a new release of RubyGems. For the past week, most of my spare time has gone into making that happen. Now its time to get back into some other projects that I’m woefully behind on …

But before we do, it’s time to have a little fun with Ruby.

A Language Based SpreadSheet

Patrick Logan wonders aloud why spread sheets haven’t made it into programming languages as first class objects. He then goes on to speculate what it might look like in Smalltalk. And along the way, he bumps into some interesting concepts about evaluating expressions.

Translating Patrick’s Smalltalk code into Ruby turns out to be quite straight forward …

  ss = SpreadSheet.new
  ss[1,1].value = 5
  ss[1,2].value = ss[1,1] * 6
  ss[1,3].value = ss[1,2] * 7
  puts ss[1,3].value             # => 210

ss is our spread sheet object. Indexing it with row and column indicies yields cells, which can hold formulas. The first cell gets a five. The second cell (at [1,,2]) gets 6 times that (30), and the final cell gets 7 times that (210).

Straight forward arithmetic, right?

Wrong!

Remember that this is a spread sheet. Changing the values in cells should effect cells that derive from it. In other words, if we change the value of ss[1,1] and then ask for the value of ss[1,3], we should get a new value.

  ss[1,1].value = 10
  puts ss[1,3].value     # Should now print 420!

The naive implementation of just storing values in arrays as we calculate them just isn’t going to hack it.

Ummm … Why Don’t We Use Lambdas?

My first thought was that we would want to just wrap the expressions in a lambda. Putting them in a lambda has the effect of deferring the evaluation of the expression until we really want it. And we can reevaluate the expression as needed as its dependents change.

The result would look like this …

  ss = SpreadSheet.new
  ss[1,1].value = 5
  ss[1,2].value = lambda { ss[1,1] * 6 }
  ss[1,3].value = lambda { ss[1,2] * 7 }
  puts ss[1,3].value             # => 210

In fact, a commenter to Patrick’s blog suggested the same thing.

Patrick responds.

The problem then is the programmer has to know where to put the blocks to delay computation and where to force the revaluations. Instead of blocks, though, my intention is to use some new object, a Formula, say, and to make those objects implicit as much as possible.

Deferring Expressions in Ruby

How would this work out in Ruby? In Ruby, all computation is accomplished by sending messages. To defer a computation, just capture its message and replay it later at your convenience. We will start with a formula object that turns any message sent to it into a deferred object.

  class Formula < Builder::BlankSlate
    def method_missing(sym, *args, &block)
      Deferred.new(self, sym, args, block)
    end
  end

Since you generally want every message sent to a formula object to be recorded, I based Formula on the BlankSlate class I’ve mentioned earlier. Deferred is also fairly straight forward to write. The initialize method just records the receiver of a message, the message name, arguments and any blocks.

  class Deferred < Formula
    def initialize(target, operation, args, block)
      @target = target
      @operation = operation
      @args = args
      @block = block
    end
    # ...

We derive Deferred from Formula because we want operations against a deferred object to also be deferred, and Formula handles that perfectly.

Now, when we want the value of a deferred operation, we need to ask it nicely. We will use a method named formula_value for that purpose.

    def formula_value
      @target.formula_value.send(@operation, *eval_args, &@block)
    end
    # ...

To replay the deferred operation, we need to get the target (reciever) of the message. Since the target was a formula, we need to ask for its formula value. We then send it the original operation (message name) and a list of arguments. Just one subtle note about the arguments. They too might (or might not) be formula objects, in which case we need to evaluate them before passing them to send. eval_args just creates a new list of formula values from the original argument list.

    def eval_args
      @args.collect { |a| a.formula_value }
    end
  end  # of class Deferred

Formulas in Action

Suppose I had a Formula object, and tried to add 1 to it. What would I get …

  result = some_formula + 1

result is a new deferred object, capturing the sending of +1 to the formula. To get the real value, we ask the result for its formula_value:

  result.formula_value

which recursively gets the formula value of some_formula and sends it a +1 message.

Something is Missing

Great. We see how to get deferred evaluations if we have a formula object, but where does that original formula object come from?

There are several options. One is to create a Formula wrapper around a normal Ruby value.

  class Const < Formula
    attr_reader :formula_value
    def initialize(value)
      @formula_value = value
    end
  end

Now we can say:

  result = Const.new(5) + 3    # Returns a deferred formula object

and later ask:

  result.formula_value         # Returns 8

Mirror, Mirror

Another question: I can see how formula+1 works. The + message is sent to a formula object and gets handled specially. But what if we write:

  1 + formula

Won’t 1 get confused because it doesn’t know how to handle a formula object?

Well, yes and no. The + operation in Integer will get confused, but it has a backup procedure to follow when it doesn’t know how to add itself to an arbitrary object: It asks the object how to do it.

Integer + will call coerce on the Formula object and expect Formula to figure out how to do the addition. Coerce should return a two element list whose elements can be added together.

Here is coerce for Formula:

  class Formula
    def coerce(other)
      [Const.new(other), self]
    end
  end

Formula just wraps the original number in a Formula wrapper and then lets the wrapper handle deferring the addition.

The SpreadSheet Cells

The Cells of the spreadsheet are Formula objects too. The only catch here is that they can hold different Formula objects over time. value should calculate the value of a cell (and will in turn call formula_value to do so). value=(val) should set the internal formula to whatever the user specifies.

Here is Cell in all its glory.

  class Cell < Formula
    def initialize
      @formula = 0
    end

    def value
      @formula.formula_value
    end

    def value=(new_value)
      @formula = new_value
    end

    def formula_value
      @formula.formula_value
    end
  end

Making a Cell object a formula is pretty key to the whole deferred calculation design. If a cell contains only normal Ruby objects, then its value can be calculated immediately. However, we want to defer calculations that depend upon other cells, and since adding a cell object to any expression will automatically defer it, we get the effect we want automatically.

Hey! Wait a Minute!

The astute observer will note that I initialize @formula in Cell to 0, but later in the code send a formula_value message to @formula. Won’t this cause problem, sending formula message to a non-formula object?

Well, yes it would. But it simplifies the code greatly if we just pretend all objects are formulas and can respond to formula_value. Non-formula objects just respond by returning themselves.

This is easy to accomplish.

  module Kernel
    def formula_value
      self
    end
  end

(And this is why I chose a rather awkward name for fetching a formula’s value. Since all objects will implement this method, I wanted it to avoid potential name conflicts).

The SpreadSheet

The final piece of the puzzle is the actual spread sheet object. Its only real function is to act as a lookup container for the Cell objects. My implementation uses a cheesy "convert two integers to a string key" technique. It works ok, but it bothers me.

  class SpreadSheet
    def initialize
      @hash = Hash.new
    end

    def [](r,c)
      @hash["#{r}@#{c}"] ||= Cell.new
    end
  end

That’s it. The guts of a spread sheet in under 100 lines of code. You can see the complete listing on my wiki.

Other possibilities

This technique of deferring calculations has some really interesting possibilities. Imagine that instead of replaying deferred calculations, we examined the deferred expression and performed some operation on them. Like what? Well, maybe optimizing the expression, maybe analyzing the variable references, maybe generating SQL from them. Remember the Criteria library … it uses this technique to translate ruby code into SQL conditions.

Limitations

Be careful with this technique. Although quite powerful, there are a couple of places that can cause problems. In particular, the && and || operators in Ruby are difficult to capture in this way.

• Feedback

I’m going to turn 30 this year.

Then I pause and let them do a double take at the graying color of my hair, and then finish with …

… hexadecimal.

The joke goes over pretty well amongst my geek and programmer friends. However, when used in non-geek company, they just look at me as if I lost my mind.

Perhaps I have.

a Ruby program

before I even notice

is already done

These are almost the exact words of one of my coworkers, who after considering Java for a particular problem, decided to use Ruby instead. He said he just started writing a little bit of code and all of a sudden he realized that he was done.

This is true in general. Both the DI and SL patterns provide containers that you pull objects out of. However, the essential difference between them is that your application code is aware of the Service Locator pattern, but Dependency Injection is invisible to the app.

So, if you take your DI container and pass it to a constructor, you are really using the DI container in a Service Locator manner. The key question to ask is: If you were to change the interface to the DI container, does your app need to change as well.

Someone else asked me how to decide between DI and SL, or just rolling your own. My answer is to look at the amount of pain you suffer on configuring your the modules[1] of your system. Ruby is flexible enough so that most projects can get by without either DI or SL. When it begins to get cumbersome managing different configurations by hand, it is fairly painless to switch to lightweight DI container such as Needle.

Note 1:

By "configuring your modules", I don’t mean supplying configuration data to your program, but deciding what modules should be selected. For example, while testing you might want to use a mock database layer instead of the real thing.

• Feedback

Creativity requires breaking out of the ruts of our minds. Working with the right person helps us to be creative because what seems normal to them is strange to us, and our usual way of working seems odd to them. Creative collaboration requires people to differ in some important way.

I certainly experienced that in several different ways over the last few weeks. The first example was my exploration into Ruby-based dependency injection. It was sparked by Jamis Buck’s presentation on Copland at RubyConf2004. I wrote up some ideas and Jamis took those bare ideas and fleshed them out into a real product (Needle) which represents the lightweight view of Dependency Injection. Evind Eklund also made some suggestions for improvements and the final result is something better that any of us would have come up with in isolation.

Another example happened this past month in the weeks after RubyConf. David Heinemeier Hansson has decided to include support for my XML Builder object in Rails. He mentioned to me that support for the processing instructions and declarations would be nice. I threw something together, but got some of the details wrong. Later that evening Rich Kilmer pops up an IM window and together we work out the rough spots in the design. Along the way, we come up with a cool way of supporting namespaces that fits well with the Builder style. It was a great session with each of us contributing and feeding off the ideas of the other.

I think Extreme Programming’s emphasis of pair programming is an attempt to tap into the creative potential of two different minds attacking a problem from different viewpoints. And it works fairly well at that. Now I’m wondering what other activities might benefit from the "two heads are better than one" approach. Maybe I’ll grab a friend and we will think about it together.

• Feedback

Introduction

I once attempted to explain DI/IoC to a room of Java programmers (see onestepback.org/articles/dependencyinjection/), so I can’t pass up trying to explain it to Ruby developers.

Thanks goes to Jamis Buck (the author of the Copland DI/IoC framework) who took the time to review this article and provide feedback.

What is Dependency Injection?

Consider the problem of putting together a moderately complex OO program. Typical OO programs create a bunch of objects, wire them together in interesting ways and then let the objects run. It is the first two steps, creating and wiring, that are addressed by Dependency Injection.

By the way, another term for dependency injection is Inversion of Control. Unfortunately, so many things in computer science are called inversion of control that the phrase does not evoke the right connotations with me, so I tend to avoid it. But Inversion of Control is the older term for this pattern so you will see it in many places.

A Moderately Complex Example

One of the problems with explaining Dependency Inversion is that DI only becomes really useful in larger projects. Using a simple example to explain DI leaves the listener thinking "But I can do that easily by (fill in the blank)". So my example is going to be a bit more complex, but hopefully not so large that the reader is unable to understand it.

Imagine you have a webapp that tracks the prices of stocks over time. The application is nicely partitioned into different modules that each handle a portion of the job. A StockQuotes module talks to a remote web service to pull down the current values of the stocks you are tracking. A Database module records the stock values over time. Because this data is highly competitive, you require a login to use the system and thus have an Authentication module to handle validation of user names and password. In addition to these "main" modules, there are a number of additional utility modules used by multiple modules: ErrorHandler to standardize the handling and reporting of error messages and Logger to provide a standard way of logging messsages.

A fully wired system might look something like this:

Building it Old Style!

In the bad, old days, we would just put the logic of building the web app directly into its initialize method. It might look something like this…

  class WebApp
    def initialize
      @quotes = StockQuotes.new
      @authenticator = Authenticator.new
      @database = Database.new
      @logger = Logger.new
      @error_handler = ErrorHandler.new
    end
    # ...
  end

That handles building the WebApp well enough, but what about the subordinate modules. How does the StockQuotes module find out about the logger and error handler, or how does the Authenticator find the database and logger?

We could rewrite WebApp#initialize to create everything in the right order and then pass the logger and error handler to StockQuotes. But that makes the web app rather dependent on details of the StockQuotes module. Currently the database module is created after the quote module, but suppose a change in StockQuotes causes it to need the database. That would require the WebApp to be aware of the change, rearrange the order of creation so that the database is created before the stock quotes module and finally make the database available to the quote service. Yuck!

Even worse, the WebApp knows the concrete name of every module it uses. If I wanted to create an instance of the WebApp for testing, I might want to provide a mock quote service so that I can control the quotes used in testing. Or I might want a mock database for testing. All of these choices are difficult because WebApp knows the class name of all its subordinates.

Enter the Service Locator

We would like to remove the explicit reference to class names in WebApp, but still allow it to locate the services it needs. The Service Locator pattern was designed to address this problem.

With Service Locator, we place references to services in one container and then pass that container to the modules that need to locate those services.

  def create_application
    locator = {}
    locator[:logger] = Logger.new
    locator[:error_handler] = ErrorHandler.new(locator)
    locator[:quotes] = StockQuotes.new(locator)
    locator[:database] = Database.new(locator)
    locator[:authenticator] = Authenticator.new(locator)
    locator[:webapp] = WebApp.new(locator)
  end

The initialize function for a service just uses the locator to find the services. Here is how StockQuotes might look…

  class StockQuotes
    def initialize(locator)
      @error_handler = locator[:error_handler]
      @logger = locator[:logger]
    end
    # ...
  end

Not bad. Now no service is aware of the exact class used for the other services. We can reconfigure the system easily by editted the create_application method.

We use the Service Locator pattern (and variations) at work in our Java system.

External Configuration

Although we built the service locator in Ruby code, it would not be difficult to specify the locator as a configuration file. A simple Ruby method could read the file, instantiate the objects and populate a hash table. This might allow non-programmers to tweak a configuration to their liking.

More Goodness

Another neat thing about the locator is that we can use it to configure data as well as modules. Suppose we wanted to specify the file to be used as the log file. We might modify the create_application method to include the following:

  locator[:log_file_name] = "webapp.log"
  locator[:logger] = Logger.new(locator)

And Logger would have to know that the log file was identified by :log_file_name in the locator. The Database module is another likely candidate for locator based information (e.g. DB user name and password, DB host name).

But …

As good as the Service Locator pattern is, there are still some negatives. Every class that uses the locator needs to be written expecting a locator as an argument to initialize method. This is not a natural idiom for Ruby programmer. In the absence of Service Locators, I would expect that the Logger class would be written like this …

  class Logger
    def initialize(log_filename)
      # ...
    end
    # ...
  end

which would make it unusable in a system that depended upon service locators.

Another downside is that all modules that use the locator must agree on the names of the services. For example, if MyLogger expects its file name to be under :log_filename and YourLogger expects to find its filename under :log_file then the two loggers are not plug replaceable.

Also, Suppose both StackQuotes and Datebase found their loggers using :logger, but we want to give them separate logger instances for some reason. The explicit dependence on the name of the logger service makes this a bit difficult.

And finally, the service locator did not solve the problem of creation order. The database is still created after the stock quotes module, causing problems if the stocks quotes module were modified to use the database.

None of the problems are show stoppers and there are workarounds for each, but it does make us wonder if there is a more general solution.

Finally, Dependency Injection

Dependency Injection is much like using service locators in that we identify the services by name. The big difference is that dependency injectors also take the responsibility of creating the service objects and making sure the dependent services are provided as needed.

This means that the services can be written in complete ignorance of dependency injection framework. All they need to do is make sure that they can be told about the services they need, either through parameters to a constructor, or through some kind of setter.

It also means that dependency injectors are a bit more complicated than service locators, since they also handle the creation of the services as well.

Dependency Injection in Action

How does dependency injection work? Generally, you create a DI container that is configured to know how to create the various services. Then you just ask for a service by name, and the container will create the serice (if needed) and give it to you.

For example, configuring a logger service is as easy as …

   container = DI::Container.new
   container.register(:logger) { Logger.new )

This says that the logger service is named :logger. The first time a logger service is requested, the block supplied to register will be called and a logger object will be created. Subsequent requests for a logger will return the already created logger.

To get a logger service, all you need to do is ask:

   logger = container.logger

If a logger requires a parameter, then you can easily handle that in the registration block.

  container.register(:logger) { Logger.new("logfile.log") }

If you would rather have the logger get its log filename from the container, you can do this …

  container.register(:logger) { |c| Logger.new(c.log_filename) }

And then somewhere else you can specify the log name …

  container.register(:log_filename) { "logfile.log" }

Configuring the WebApp with Dependency Injection

Now that we’ve seen some DI in action, let’s try it on our web app …

  def create_application
    container = DI::Container.new
    container.register(:logfilename) { "logfile.log" }
    container.register(:db_user) { "jim" }
    container.register(:db_password) { "secret" }
    container.register(:dbi_string) { "DBI:Pg:example_data" }

    container.register(:app) { |c|
      app = WebApp.new(c.quotes, c.authenticator, c.database)
      app.logger = c.logger
      app.set_error_handler c.error_handler
      app
    }

    container.register(:quotes) { |c|
      StockQuotes.new(c.error_handler, c.logger)
    }

    container.register(:authenticator) { |c|
      Authenticator.new(c.database, c.logger, c.error_handler)
    }

    container.register(:database) { |c|
      DBI.connect(c.dbi_string, c.db_user, c.db_password)
    }

    container.register(:logger) { |c| Logger.new(c.logfilename) }
    container.register(:error_handler) { |c|
      errh = ErrorHandler.new
      errh.logger = c.logger
      errh
    }
  end

As you can see, it is a bit more complicated than the service locator. The main reason for the complexity is that we have moved the creation logic out of the services and into the DI container. What we have gained is the ability to inject dependencies into any object without having to make special code changes to support it.

Just a few closing notes:

• Both constructor injection (StockQuotes) and setter injection (ErrorHandler) or a combination of both (WebApp) can be supported with this framework.
• We can even handle cases where the creation method is not named "new" (DBI).
• If a poorly written service didn’t provide a way to inject the services it depends upon, we could use instance_variable_set to force a dependent service into place. Obviously, this would be less than desireable.
• The order of the registration doesn’t matter, since no service is created until everything is registered. If the StockQuotes module suddenly starts needing a database connection, no problem. We just add a reference to a database service in the creation code for StockQuotes and we are done. The DI framework worries about making sure the database is created before anything that needs it.
• The container doesn’t have to be configured in one place. For example, we could move the first four register calls to a separate file that would allow the log file and database information to be modified independently of the rest.
• There still needs to be agreement about service names, but now only the container knows about them. The individual services don’t care.
• Since the DI container is responsible for all the service names and service creation, it is easy to intercept a service and wrap an AOP-like wrapper around a it.
• Just like the service locator, a DI container could be configured through a configuration file. The configuration would be more complex (because the DI container is more complex), but still quite doable. Another idea is to use Ruby as Domain Specific Language for DI container configuration.

Summary

Both the Service Locator and Dependency Injection patterns are quite useful, but each has different tradeoffs between flexibility and complexity. Understand the differences and you will have all you need to choose the proper idiom for and give circumstance.

You can find the example framework and unit tests here:

• depinj.rb
• testdepinj.rb

• Feedback

Narf: revisiting a 2 year old (Patrick May)

Narf (Not Another Ruby Framework) is a web framework for Ruby. Patrick introduced Narf at an earlier RubyConf. The latest Narf seems to have added a number of libraries and facilities over the past few years.

One of the really interesting points in Patrick’s presentation is how he handles vandals at his wiki site. He has created a tarpit, so that known vandals are redirected to a parallel web site that gets restored every night. The vandals believe they are modifying the real site, but no one else sees the vandals changes.

Another thing to look into is the HtmlArea library for doing rich text form editing in a browser.

ruby-doc.org: Now and the Future (James Britt)

The ruby-doc site was born at the Seattle RubyConf then James Britt and Jim Freeze talked about pulling together documentation for the Ruby community. The site has grown over the years and provides some great information. The biggest downside to the site is the difficulty finding and and navigating the information. James talked about approaches to categorizing information automatically and easily.

(an aside)

Bruce Williams has created a web site for pasting code. There is a section for RubyConf folk to share code. See codepaste.org.

By the way, codepaste is a Rails application, which leads us to …

Ruby on Rails … Origin, Driver, Destination (David Heinemeier Hansson)

David shares how he discovered Ruby and had this wonderful experience with it. Rails, in part, is an attempt to bring the joy of Ruby to the masses by providing an attractive,easy to use web framework.

If you have not seen Rails, check out the ten-minute introduction flash video at media.nextangle.com/rails/rails_setup.mov.

Hang on! There is a rails surprised promised after everybody gets their lunch food.

Lunch Break

(over the shoulder)

I’m sitting behind Rich Kilmer at the conference. I just saw him bring up a web page, pause with the mouse over the submit button and glance over at Chad. He then pressed submit. I think I just saw the first upload of Alph software to RubyForge. Let’s check this out (browses over to RubyForge). Yes, it’s there! Download Alph

The Many Facets of RubyGems (Jim Weirich

What can I say. I think it went well. You can see everything at onestepback.org/articles/rubygemsfacets.

YARV: Yet Another Ruby VM (SASADA Koichi)

Despite an obvious language barrier, Koichi did a great job of communicating with the conference crowd. He showed a great sense of humor. Furthermore, he brought greetings from Matz (who couldn’t make it this year due to the soon to be birth of his child).

YARV is Koichi’s attempt at a VM for Ruby code. If YARV is successful, it will become the Rite used for Ruby 2.0. This is really exciting to see progress in something that might become Rite.

Some properties of YARV include:

• Simple stack machinge
• Ruby C extension
• Not bytecode, but wordcode
• Use Ruby’s existing infrastructure (e.g. gc, parser, API).
• YARV traverses the AST to generate code.

Currently, there are a number of basic Ruby operations that aren’t supported (method_missing comes to mind). Over the next few months Koichi will be implementing these missing feature, and also implementing the JIT and AOT (Ahead of Time) compilers for YARV. YARV will also compile direct to C code.

We wish Koichi good luck in his goals!

"Test::Unit".downcase.sub(/::/,"/") (Nathaniel Talbott)

Nathaniel shared some insights into his understanding of the "Ruby Way" and how it has changed over the years. He has applied these insights toward building a more Rubyesque testing framework.

Stuff coming to test/unit:

• Easier to write parts of the test suites (runners, assertions, etc)
• Reloadable runners.
• Using test metadata
• Declarative test syntax (i.e. a Domain Specific Language for specifying tests).

    suite do
      setup { ... setup stuff ... }
      setup_once {  ... setup once ... }
      t do
        assert_this ...
        assert_that ...
      end
    end
  

• Inline test that exist in the same file as your code.
• The ability to put examples in your class and use them as documentation.
  • e.g. example { assert_equal 2, Adder.add(1,1) }

I’m really excited about these changes. Testing in ruby is already easy, but these changes will make it even more flexible. Cool!

Surprise Presentation (Shashank Date)

Bill Venners has contacted the Ruby community about creating a web-based zine focused on Ruby. Shashank has agreed to be the editor and he has an advisory board to help him review the submitted articles. This is just a pre-announcement, there will be something more formal around the first of the year.

(RubyConf Blackout)

Sometime during the afternoon internet access through the wireless link was lost. I can only imagine the reaction in the rest of the Ruby world as suddenly everyone at the conference went silent on the #ruby-lang IRC channel. We’re back now, but I still don’t know about the details.

Dinner … Meal supplied by Infoether

Objective-C: A Retrospective (Brad Cox)

Mr. Cox started with a review of Objective-C, some of its history and some small details of its implementation. Objective-C is used to write most of the Mac software these days.

After the Objective-C talk, Mr. Cox explored some ideas in the nature of software economics. He made the following observations.

• Hardware is made of atoms
  • Abides by physical convservation lays
  • You can buy, sell and own it
• Software is made of bits
  • Immune to physical conservation laws
  • You can’t buy, sell and own it.
• Implications
  • Copyright based compensation cannot work
  • Advertising based compensation (TV model)
  • Useright base compensation never tried.

Given the above, Mr. Cox is advocating a pay-by-use/micropayments system where some kind of accounting system tracks the number of times you call a function (string compare for example) and charges your bank account for the use. Considering that a good portion of the conference attendees are open source advocates, there was a good deal of push back on these ideas. I think I see where Mr. Cox was going, he wants to create an economic system that pumps revenue into the creation of software. Unfortunately, I’m not convinced that his approach really addresses the non-tangible nature of software that he identified earlier. Nevertheless, he provided some food for thought.

You can see some of Mr. Cox’s ideas at virtualschool.edu/mybank/

Evening Activities

After the keynote talk, a good number of attendees migrated to the hotel lobby (where they have WiFi access). I didn’t see a lot of programming, but there was a lot of conversations. I started out by catching up with David Black, and then spent some time with Shashank showing him RubyGems and talking about Rake. Shashank wants to use Rake to control distributed processes, so we experimented with spawning threads from within Rake. The next step would have tasks sending commands to Rake-like Drb servers to run jobs on remote systems. It really won’t be hard to do at all.

• Feedback

RubyX (John Knight)

John gave a short presentation about the RubyX project, which is a linux distribution that uses Ruby in some manner. I’m a little unclear on exactly how Ruby is used in the project, but John is advocating that folks who are interested take a look at it and supported it.

Ruby on Windows (Dan Berger)

Dan has been using Ruby on windows and realized Ruby seriously lagged behind both Perl and Python in supporting the windows platform. Dan has been working on the win32util project on RubyForge to address that disparity. Daniel did include the disclaimer that he is not a Microsoft Employee, nor is he paid for this

Dan first talked about setting up services. I’m grabbing a lot of his example code because I have an immediate use for this.

To query about services …

  require "wind32/service"
  include Win32
  Service.services { |service| p service}
  Service.status("ClipSrc")
  Service.getdisplayname("ClipsSrv")

To control a service …

  Service.stop(name)
  Service.start(name)
  Service.pause(name)
  Service.resume(name)
  Service.delete(name)

To create a service …

  require 'win32/service"
  include Win32

  class MyDaemon < Daemon
    def service_main
      # Service code goes here
    rescue Exception => e
      logfile.puts "ERROR: #{e.message}"
      exit
    end
  end

  d = MyDaemon.new
  d.mainloop

To register a service

  serv = Service.new
  serv.create_service { |s|
    s.service_name = "aba"
    s.display_name = "aba"
    s.binary_path_name = "c:\\..."
  }

Daniel covered a number of other utils. In particular he identified a number of things that just work differently, but they are working on unifying the APIs between the two platforms. In particular, the RubyGems team is interested in the popen3 api so that our functional tests could be run on a Windows platform.

How Dynamic Can You Get? (Jamis Buck)

Jamis had the challenging task of convincing a bunch of dynamic language enthuisists that dependency injection can make their already flexible language even more flexible. While dependency injection in a huge advantage in a language like Java, there some questions to how much it adds to Ruby. Copland, a framework for Dependency Injection/Inversion of Control, is very patterned after a Java based framework. I think it would be interesting to Ruby-ize the framework and see what falls out.

Code generation with Ruby in a heterogenous network application (Gorden James Miller)

Gorden needed to get a largish C++ application running on a hardened computer network with a small memory footprint. There are a number of messages involved in the network solution. He used XML to describe the nature of the message and the structures sent with the message. Reading the XML with REXML, he used ERB to provide templates for C++ code generation to handle the messages. I found it fascinating to use ERB for code generation rather than web pages.

There are some more interesting details the type of network they are testing/simulating. The network is only up for brief periods of time and must survive as much as a 90% packet loss.

Lunch

Self-Organizing Afternoon Activities

After lunch, the afternoon was open for talking, programming or whatever else suits your fancy. Here’s some of the stuff I participated in.

• Jim Freeze and I (and later Rich Kilmer) worked up a reasonable Ruby-based domain language for Jim to use to specify some work related config files. This is one of the themes I heard over and over again during the conference.
• David Heinemeier Hansonn decided to include a "Builder style" view into Rails. If your view directory contains a ".rbuild" file, then the file will be invoked with a XML Builder object that you can use to programmatically build your html page. This is an alternative to the rhtml ERB files. Builder probably isn’t a good choice where you have a page designer involved, but it might make sense for a programmer only project, or for generating an RSS style page. David also mentioned something about doing web services with Rails. Now that would be cool.
• Finally, I worked with Chad Fowler and Bruce Williams on the design of the new RubyGems.org website. Chad had a prototype app built, and Bruce started helping him refine it Me? I kibitz-ed and watched for the most part.

Conference Summary

What a weekend! There was an energy about this conference that I hadn’t felt before. The entire community was excited about apps like Rails and the proto-Rite VM (YARV). The ability to talk to folks actually using your software and getting feedback is quite a rush. I received all kinds of good ideas and suggestions. Unfornately, my plate is already full of things to do, so who know when I will get to all these ideas.

Wow, I can’t wait till next year!

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Conference Introduction

David Black did his usual "Welcome to RubyConf" thing. Sounds like one or two presenters didn’t make it, so we will be doing some creative scheduling. The new PickAxe books are here, but they won’t be handed out until this afternoon (boo hiss). Oh, well.

Teaching Ruby in a Corporate Environment (Jim Freeze)

Jim is working for an EDA company. His company has established Ruby as the "knighted" language for development in this company consisting of mainly Electrical Engineers. Jim has a 3 day course on teaching Ruby to the EEs. It is oriented toward coding neophytes. I really appreciated his examples that were targetted for particular kinds of engineers.

Ruby as Maestro (Rich Kilmer)

Rich’s talk was a last minute addition to the presentation list to make up for a missing presenter. Rich’s company used Ruby to automate a component based blackboard system running on more than 300 nodes. The active agent program is a huge distributed java program, but Ruby is used to configure, build and control the system.

Rich’s project uses one of my favorite features of Ruby … the ability to create domain specific languages for specific purposes.

  wait_for "SocietyQuiesced", 2.hours do
    do_action "StopCommunications"
    do_action "StopSociety"
  end

(an aside)

There seems to be a running commentary on IRC #ruby-lang if you want to listen in.

Lunch Break

Using and Extending Ruwiki (Austin Ziegler)

Ruwiki looks like a very promising wiki clone. I’ve considered using it for my comments page. Ruwiki is very extensible (tweakable markup, different markup engines, different storage backends, etc.).

(another aside)

Bill Kleb from Langley just asked for help getting Ruby to run on the IA64 architecture.

Tycho: A Proposed Ruby-based PIM (Hal Fulton)

Hal talks about his implementation of a Personal Information Manager inspired by Info Select (a.k.a. Tornado). Tycho looks like a rather interesting way to organize information. The executable node feature could do some really interesting things (I’m thinking of a contact list that could dial your phone for you … Ok, that’s lame, but you get the idea)

Pickaxe II

Woohoo! Time to hand out the PickAxe II books.

Hacking Ruby (Paul Brannon)

Paul shares some ideas about hacking ruby code … i.e. messing around with Ruby internals, changing the meaning of built-in functions and classes, and generally having fun.

Alph (Rich Kilmer)

         In Xanadu did Kubla Khan
      A stately pleasure dome decree
    Where Alph, the sacred river, ran
    Through caverns measureless to man
           Down to a sunless sea.

Alph is a Ruby/Flash bridge allowing you to write Ruby code to control a flash application. Now that sounds simple, but there are really "interesting" hoop Rich had to jump through to get here.

Rich always thinks big. MacroMedia’s new license scheme for the layout managers makes it impossible to use layout managers with Rich’s scheme (without paying a lot of money). So, Rich is thinking about implementing an open source component library to run on the Flash VM. (note to self: Never piss off Rich)

After Conference Activities …

The formal part of the conference was over around 9:30 and we had to vacate the meeting room so that the hotel could lock it up. A large fraction of the conference attendees drifted into the hotel lobby and claimed any spot that was near a power out to continue talking and hacking. Here’s a quick rundown on some of the mini-gatherings:

• Charlie Mills was helping Bill Kleb get Ruby compiled for the IA64 archtecture. Charlie is the fellow who helped Rich Kilmer and Chad Fowler with their DNSSD service wrapper at OSCON this year. It looked like Bill and Charlie had some success by disabling optimization on the C compiler.
• At least on person was working on their presentation for the next day.
• There was a fairly large group talking to Charles L. Perkins regarding the history of Smalltalk. Charles was involved with the early Xerox Parc Place developers and had some good inside stories about the early days of Smalltalk. Later when I dropped by it sounded as if they had moved past Smalltalk history and were discussing some of the capabilities of Prolog.
• Right next to the Smalltalk history group was another cluster of folks watching as David Heinemeier Hansson helped Jim Freeze through a tutorial on Rails. I’ve used Rails a little bit and am very impressed with the framework. When I dropped by, Jim had just got a login screen working for the demo weblog.
• Chad Fowler was helping Shashank Date work on Gemifying some of the windows tools that Shashank is planning on releasing. This is where I landed for a while. By the end of the evening, we had Shashank’s WxRuby application running as a gem.

Oh, and by the way, it looks like Genx4R is the 100th ruby app/library to be packaged as a Gem.

(More Ruby Fun tomorrow)

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If we hit 100 before my talk tomorrow, I will add a mention of that Gem to the presentation (how about that for motivation).

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