I recently applied this great plugin a few times to tackle different tasks and would like to share with you the joys of thinking in state machines!

Disclaimer: This installment is ‘just’ an intro to the topic (a teaser if you like), it doesn’t contain actual instructions or code on how to use actsasstate_machine - that comes in part II. Though the original intent was to write up a small tutorial with some example code, I started with an intro and the article grew so long that I decided to split it up - so stay tuned for part deux!

State what…?!?

A finite state machine (FSM for short) a.k.a. finite state automaton (FSA) is a 5-tuple (Σ,S,s₀,δ,F)… OK, just kidding. I doubt too much people are interested in the rigorous definition of the FSM (for the rest, here it is), so let’s see a more down-to earth description.

According to wikipedia, Finite state machine is “a model of behavior composed of a finite number of states, transitions between those states, and actions“. Somewhat better than those gammas and sigmas and stuff but if you are not the abstract thinker type, it might take some time to wrap your brain around it. I believe a good example can help here!

Everybody knows and loves regular expressions - but probably it’s not that wide known fact that regular expression matching can be solved with an FSM (and in fact, a lot of implementations are using some kind of FSM on steroids). So let’s see a simple example. Suppose we would like to match a string against the following, simple regexp:

ab+(a|c)b*

First we have to construct the FSM, which will be fed with the string we would like to match. An FSM for the above regular expression might look like this:

String matching against this FSM is basically answering the question ’starting from the initial state, can we reach the finish after feeding the FSM the whole string?’. Pretty easy - the only thing we have to define is ‘feeding’.

So let’s take the string ‘abbbcbbb’ as an example and feed the FSM! The process looks like this:

1. we are in q0, the initial state (where the ’start’ label is). Starting to consume the string
2. we receive the first character, it’s an ‘a‘. We have an ‘a‘ arrow to state q1, so we make a transition there
3. we receive the next character, ‘b‘. We have two b-arrows: to q1 and q2. We choose to go to q1 (in fact, staying in q1) - remember, the question is whether we _can_ reach the finish, not whether all roads lead to the finish - so the choice is ours!
4. identical to the above
5. after the two above steps, we are still in q1. We still get a ‘b‘ but this time we decide to move to q2.
6. we are in q2 and the input is ‘c‘. We have no analysis-paralysis here since the only thing we can do is to move to q4 - so let’s do that!
7. Whoa! We reached the finish line! (q4 is one of the terminal states). However, we didn’t consume the whole string yet, so we can’t yet tell whether the regexp matches or not.
8. So we eat the rest of the string (the ‘how’ is left as an exercise to the reader) and return ‘match!’

Let’s see a very simple non-matching example on the string ‘abac’

1. in q0
2. got an ‘a‘, move to q1
3. in q1, got a ‘b‘, move to q2
4. in q2, got an ‘a‘, move to q3 - we reached the finish, but still have a character to consume
5. in q3, got a ‘c‘… oops. We have no ‘c’ arrow from q3 so we are stuck. return ‘no match!’

Of course the real-life scenarios are much more complicated than the above one and sometimes FSMs are not enough (for example to my knowledge it’s not possible to tell about a number whether it is prime or not with a vanilla FSM - but a regexp doing just that has been floating around some time ago) but to illustrate the concept this example served fine.

This is cool and all but why should I care?!?

Well, yeah, you are obviously not going to model an FSM the next time you would like to match a regexp - that would be wheel-reinvention at it’s finest. However there are some practical scenarios where an FSM can come handy:

• sometimes the logic flow is just too complicated to model - an if-forrest is rarely a good solution (on the flip side, don’t model an if-else with an FSM )
• encapsulate complex logic flow into a pattern and not clutter your code with it.
• you are in a stateless world - for example HTTP
• asynchronous and/or distributed processing where you explicitly need to maintain your state and act upon it

Some real life examples of FSM usage in the Ruby/Rails world are why the lucky stiff’s Hpricot (using Ragel) or Rick Olson’s restful authentication plugin (using actsasstate_machine)

The Next Episode

In the next installment I’d like to focus on the practical usage of the actsasstate_machine plugin - I’ll attempt to create an asynchronous messaging system in a Rails app using it.

• Easy git-svn for Rails - I really can’t imagine how could it be easier to move from svn to git. Really no more excuses!
• Writing Your Own Front Controller for Rails - forget about routes.rb. A less drastic solution is the Catch-all Route.
• Sidebars and Other Dynamic Content - Dynamically filling elements of your layouts. (Additional stuff to the railscast “5 View Tips”).

Light & Shadow is a ProtoType-based library for creating great looking drop shadows easily. Check out the HTML I used to generate the example image and see it yourself that it’s not rocket science!

All you have to do is to set up a light source with a few parameters (distance, intensity, size etc.) and add the class ’shadowThrowing’ to your elements which should… well, throw shadows . I won’t go into details here, you can find the explanation and other details on the Light & Shadow project page.

(Found via Gedankenkonserve - thanks Bernhard )

I have been always uncertain about the exact expression denoting today midnight (or any day midnight, for that matter). Is 00:00 on e.g. April 24th the midnight between 23rd and 24th or 24th and 25th? If I want something to happen at today midnight, is that today’s date at 00:00? (for the impatient: no, it isn’t ).

Chronic to the rescue! (If you don’t know chronic, be sure to check it out - it’s a great natural language date/time parser). All I had to do is:

>> Chronic.parse('today midnight')
=> Fri Apr 25 00:00:00 +0200 2008

so actually it turns out it’s tomorrow’s date at 00:00.

I couldn’t find time zone support though (I am not saying it’s not there, just that I couldn’t find it by looking at the API) - so what if I want to meet someone in Madrid today midnight? Why, I install the tzinfo gem and ask Ruby!

>> TzinfoTimezone["Madrid"].utc_to_local(Chronic.parse('today midnight').getutc)
=> Fri Apr 25 00:00:00 UTC 2008

• AI Ruby plugins (via rubyflow.com) - list of AI related libraries for Ruby. Parsing, Machine Learning, Semantic stuff…
• Programming Collective Intelligence Python to Ruby translation - I guess a lot of people here read
  Programming Collective Intelligence from Toby Segaran. I can only recommend it - it’s a great book, and now even better with Ruby source code

• Git and Ruby Tutorials - a great collection from rubyinside.com, also the comments contain a few good pointers.
• 
  acts_as_dropdown - acts_as_dropdown allows any ActiveRecord class to be easily used as the contents of a HTML select tag.
• Handling JavaScript Events on Multiple Elements - proper JS/Prototype event handling!
• tranexp - Dr. Nic in action again. This time it’s a dead simple translator gem.

Update: Sergio, the author of the livevalidation rails plugin updated the plugin so you can disregard the finale of the article (validatesconfirmationof is working, as well as the newest version of livevalidation, 1.3 is used in the plugin - so no additional tweaking is needed, install and validate away )

Surely I am not the only one who was a ‘bit nervous’ (that was a mild euphemism) when his carefully entered data disappeared after submitting a form to the server. Nowadays web applications are doing better than that - valid data is saved and only the problematic fields are pointed out.

Of course even that feels so 1990’s now. A contemporary (ehm… web 2.0?) web application is expected to validate the form on the client side already (WARNING! That doesn’t mean at all you shouldn’t validate on the server side though - client side validation is for the good guys but you should still look out for the script kiddies et al), pointing out the errors on the fly so there is no need to come back and change/edit those fields after submitting a form.

My library of choice is livevalidation, which has a Rails companion too - if you are using Rails form helpers and standard validation on your models, you don’t have to touch anything just install livevalidation (=drop it to your javascripts folder, it’s a single .js file). w00t!

The only major shortcoming (from my POV) of the Rails plugin is that validatesconfirmationof is not implemented. However, it’s easy to add it via standard javascript:

<input id="user_password" name="user[password]" size="30" type="password" />
<input id="user_password_confirmation" name="user[password_confirmation]" size="30"> 
<script type="text/javascript">
var validate = new LiveValidation('user_password_confirmation');
validate.add( Validate.Confirmation, { match: 'user_password' } );
</script>

That’s it!

One more note: the Rails plugin contains version 1.2 but there is a newer version, 1.3 so be sure to replace it.

Long-time Mac users probably have different solutions for this problem, but as a newbie, the screen going dim after a certain period of time - without an intuitive way to switch this off - drove me crazy! I wanted to enjoy my slideshow, video, presentation, reading something etc. and suddenly it all went dark. Arggghhh.

So I was delighted when I found

Caffeine, a super-light program sitting in your menu bar that prevents your Mac from going to sleep/starting screen savers.

Note that Caffeine doesn’t help if you close the lid - if you want your Mac to stay awake in this case, InsomniaX is your thing - it disables the sleep when closing the lid so you can listen to music/control your Mac with the remote etc.

• RubyFlow - Peter Cooper (of RubyInside fame) created “RubyInside’s sister site” - RubyFlow. Hope it takes off!
• Thinking Sphinx Reborn - I thought a phoenix is the creature with the reborn ability - though that doesn’t mean a sphinx can’t do that! btw. “Sphinx is a very fast search engine that indexes data and provides flexible ways of searching it.”
• Rails vs Merb - “The conclusion is simple, I recommended that my client go with Merb”.
• RubyAMP - powerful looking Ruby TextMate bundle.

Since I bought my Mac, Safari has been my primary browser of choice. I have been using Firefox sporadically too - you can’t do serious web development without FireBug! Safari is light, zippy and renders wonderfully looking OS X look’n'feel pages - however with the arrival of Firefox 3 I am really pondering to ditch it in favor of FF (still no OS X look in there, tho’ ). Firefox 3 beta 5 is just phenomenal - fast, powerful, and it has all the stuff I am missing from Safari (FireBug, del.icio.us toolbar, DOM Inspector, ton of other extensions) so I am really thinking that I will remain a Safari user on my iPhone only.

However, FF3 is missing some functionality I am depending on - most notably jssh support - DOM inspector was removed too, but can be installed as an add-on, and since beta 4 FireBug is working, so no major hurdles there. However, jssh, as usually was a harder nut to crack.

Fortunately Angrez, FireWatir’s author pointed me to the right direction - which was in this case compiling Firefox 3 with jssh support! Here’s how:

• Download the latest tarball (currently Firefox 3.0b5) from the FireFox source code ftp
• Follow these steps up to the 3rd point
• My .mozconfig file - assembled from this post and the mozilla developer docs
  (put it into our home folder)
• Compile time!

  cd mozilla; make -f client.mk build
  

  1. cd mozilla; make -f client.mk build
That’s it! Easy, huh?

Sit back, enjoy your coffee and in a few minutes you’ll have your own, new hot FF build with jssh support!

By the way, FireWatir 1.1 hit the streets just today! Grab it and let the testing commence!

There is a great number of possibilities to do this in Ruby (just to mention a few: standard net/http, curb, mechanize, rio etc.). I have chosen a semi-standard way (=no need to learn new syntax, but definitely simpler than net/http): open-uri.

require 'open-uri'

open('target.file','w') {|f| f.write open("my.url.com/source.file", :http_basic_authentication=>['ueser', 'pass']) }

I am using Ruby for more than 2 years already but it’s succinctness still keeps me amazed!

• amatch – String Matching Extension for Ruby - Levenshtein edit distance, Sellers edit distance, the Hamming distance, the longest common subsequence length, the longest common substring length, and the pair distance metric
• Screencast on Ruby 1.9 features - it’s time to play with 1.9!
• Sustainable Development in Ruby - interesting looking series on some advanced Ruby stuff. Part 1 and Part 2 are out already!
• The nicest git tutorial I have seen so far. The author claims “Git is right for every project” - hmm…
• Static pages for the enterprise - well written article, and definitely not just for the enterprise
tags:

Quite a few blogs covered EuRuKo talks (for example here, here, here or here) so I am not going to do an n+1-th writeup. Instead I collected a few quotes I found interesting and/or funny. Without further ado, here we go:

Matz: Ruby - Past, Present and Future (Keynote)

• Chad Fowler wrote a book ‘My Job Went to India’ - and yesterday my luggage went to Oslo!
• Ruby was a hobby that came from not having a job after end of Japan’s bubble economy
• I consider myself as no great programmer!
• Then we have this nasty snake language here… (sampling through different languages starting from COBOL)
• Python people love to be organized and have one true way. Ruby people don’t care.
• (after going through a ton of different languages and finally arriving at Ruby) Ruby is not perfect either… but it’s close!
• We will need to keep Ruby alive when Rails will be gone… Hopefully Ruby will be around in 15 years, but Rails… hmm…khm… never mind.
• 10 years ago - Ruby? What’s That? Language? See This Cool Java!
• 5 years ago - Ruby? I’ve Heard of It. But I haven’t Used It YET.
• 2 years ago - Ruby! I Know! It’s for Rails, Right?

Koichi: Merging YARV is not a goal but a start

• (Running around in a t-shirt ‘No Ruby No Life’) My version: No Ruby no Job!
• 1st slide: [some completely different slide than his real topic title] - this is just a joke, the presentation is not on this
• I don’t speak English so I wrote down everything on the slides… unfortunately most of the slides are in Japanese! (LOL)
• Please ask questions in Japanese/C/Ruby! … or use slow/short English
• I have a lot of slides (hm, like 50) of different optimization techniques but it’s just too much so I won’t show you here
• My PhD thesis is in Japanese (Efficient implementation of Ruby VM), so please learn Japanese if you’d like to read it
• NT means not Windows NT but Native Thread
• Ruby thread and native thread: (shows a brutally complicated slide, fully in Japanese) and I would like to point out this part (clicks a button, and a red frame appears around a portion of fully Japanese text)
• This is complex so I skip it (after the 10th incomprehensible slide)
• I can’t program in Ruby!
• Come to Japan/Enter my Lab (please teach me English) - Unfortunately I can’t employ you because there is not enough money, so please bring your own $
• (response to a question about YARV’s memory need:) Yes, YARV also needs memory to start the VM! (considers the question answered. When asked for further details:) How much? hmm… you need to measure yourself

Charlie Nutter, Tom Enebo: JRuby - Ready for Action

• Java != a dirty word!
• Did you see this demo already? No? Good. Everybody has seen this 100 times in the US so they are really sick of it!
• See? new is on the right side of the class name!
• I love swing (after listing 9342923 looooong fuctions of the Button class)
• this would take 6-7 lines of Java (after adding a listener to a button in 1 lines of Ruby syntax)
• This is the weirdest error I have ever seen during a demo! I guess Mac OS X is not ready for this stuff yet (after not being able to kill off a process which slowed down his machine)
• Kill that bird!!!! (after thunderbird jumping around for like 5 minutes after OSX bootup)
• ColdFusion is not a fine example for anything (Charlie, after a guy proposing CouldFusion as an example of… I don’t remember what but it doesn’t matter)

Disclaimer: Please take the above with a grain of salt - it might seem based on the above sentences (which were taken out of context and possibly squeezed/lost in translation) that Koichi’s topic was to pursue people to learn Japanese (not true, his talk was very interesting and deep) or Matz was making fun of/mocking Python (not true, he was just joking all the time) etc. If you have some more, drop me a comment!

EuRuKo 2008 is over… I have had a really great time, both as an organizer and an attendee, and can’t wait for next year’s conference!

Until that gets sorted out (currently Spain (Madrid) and Poland (Warsaw vs Krakow) are competing) here are some photos we made with Marianna… They were usually made in a hurry and/or dark so don’t expect too much (I guess I should invest in a better objective and flash )

You can check out all the (correctly tagged) EuRuKo 2008 photos here.

Please post your photos to flickr or whatever service you are using, and leave a comment here with the address… Cheers!

In my quest to whip my feed reader’s Ruby/Rails related content into shape a bit, I made a little research to find out which Ruby/Rails blogs are the most popular at the moment. I had given up on following most of the blogs systematically a long time ago - it is becoming increasingly hard to keep track of even the aggregators, not to talk about the blogs themselves. There are hundreds of Ruby/Rails blogs out there right now (I am talking about the ones found on the few most popular aggregators - in reality there must be much more of them), so it is clear that you need to pick carefully - unless you happen to be a well-paid, full time Ruby/Rails blog reader (in which case you still would have to crank a lot to do your work properly).

OK, enough nonsense for today - let’s see the results counting down from the 10th place! If you are interested in the method they were created with, or a longer, top 30 list from technorati and alexa, check out this blog entry.

10. http://weblog.jamisbuck.org/ by Jamis Buck.

Jamis Buck “is a software developer who has the good fortune to be both employed by 37signals and counted among those who maintain the Ruby on Rails web framework”. He is mostly blogging about (surprise, surprise!) Rails - of course on a very high level, which could be expected from a Rails core developer. Very insightful posts on ActiveRecord, Capistrano and other essential Rails topics delivered in a professional way.

9. http://weblog.rubyonrails.org by the Rails core team

This is the “default” Ruby on Rails blog, used for announcements, sightings, manuals and whatever else the RoR team finds interesting .

8. http://www.slash7.com by Amy Hoy.

This is a really cool little site - Amy is a very gifted writer and designer, publishing very insightful articles as well as the nicest (hands down!) cheat sheets about different Web2.0, Ajax, Rails and that sort of stuff. Definitely worth checking out!

7. http://errtheblog.com by PJ Hyett and Chris Wanstrath.

A very serious blog of two Rails-geeks about advanced topics (but very well explained - so if you are not totally green (#00FF00) you should do fine). Among other things, they have contributed Sexy Migrations to Rails recently.

6. http://nubyonrails.com/ by Geoffrey Grosenbach

Geoffrey is the author of more than twenty of Rails plugins, (including gruff, my favorite graph drawing gem), a horde of professional-quality articles and the PeepCode screencast site. Do I need to say more?!

5. http://redhanded.hobix.com/ by _why the lucky stiff.

_why is probably the most interesting guy in the Ruby community. He is the author of (among tons of other things) Why’s Poignant Guide to Ruby, HPricot, the coolest Ruby HTML parser, Try Ruby! (a must see!) and Hackety Hack, for aspiring wannabe programmers who want to hack like in the movies! The list goes on and on… This guy never stops. If someone will ever invent the perpetuum mobile, he will be it (in Ruby, of course).

4.http://hivelogic.com/ by Dan Benjamin.

Dan’s recent work include Cork’d, a web2.0 wine community site or the A List Apart publishing system. He does great podcasts with various guys.

3. http://mephistoblog.com/ by Rick Olson and Justin Palmer

Personally I was quite surprised that a blog concentrating on such a narrow topic (in this case the mephisto blogging system) could grab the 3rd place - so I have checked both alexa and technorati by hand just to be sure, and it seems that everything is OK - mephistoblog is ranked very high on both of them, justifying this position. After all, mephisto is the leading blog system of Rails!

2. http://www.rubyinside.com/ by Peter Cooper.

This blog is my absolute favorite from this top 10 list (actually, from all the Ruby blogs I have encountered so far). I am definitely with Amy Hoy, who said If you had to subscribe to just one Ruby blog, it should be this one. If you would like to know what’s happening in the Ruby/Rails community, rubyinside is the place to check. If there is no new post here, it’s because most probably nothing happened!

And the winner is: http://www.loudthinking.com/ by David Heinemeier Hansson.

Well, what should I add? David is the author of Ruby on Rails, so no wonder his blog topped the list!

Conclusion
It’s interesting to note that nearly all the blogs listed here are mostly pure Rails ones - rubyinside (mixed Ruby/Rails) and redhanded (pure Ruby) being the two exceptions. It would be interesting to generate such a list for Ruby blogs - though I am not sure how. The sources I have used (most notably rubycorner) aggregate both Ruby and Rails blogs) - so it seems there are much more Rails bloggers out there (or they are much better (with the exception of _why) than the Ruby bloggers).

I would really like to hear your opinion on this little experiment - whether you think it makes sense or it is completely off, how could it be improved in the future, what features could be added etc. If I’ll receive some positive feedback, I think I will work on the algorithm a bit more, and run it once in say every 3 months to see what’s happening around the Ruby/Rails blogosphere. Let me know what do you think!