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Wednesday, October 17, 2007


Rubber dinosaur 03 by watz from flickr (CC-NC-SA)
I'm not talking about Fortran, I'm talking about the actual reptiles here. Or protobirds. For as long as I can remember I believed that fossilized bones are just a poor substitute for real genetic information and people use it only because dinosaurs happened to die out without living too many descendant lines. But having seen this BBC documentary I was shocked how much behavioral information they could get from just a bunch of bones plus some experimentation. In addition to scientific value it's simply awesome. Links: part 1, part 2.

Tuesday, October 09, 2007

Two months with Ruby on Rails

Migraine! by annia316 from flickr (CC-BY)
I've been coding Ruby on Rails for the last two months and this rant is long overdue. There are just so many thing that are wrong with Ruby on Rails. Being better than PHP or J2EE is not enough to get away from a quick bashing on my blog.


I don't hate HAML any more. Total hatred was my first reaction to it but I more or less got used to it. The main problem with HAML, RHTML and probably all other solutions is not providing any sort of XSS protection. Hand-escaping all strings in views is almost PHP SQL injection hell all over again. The few times one needs to insert raw HTML in the output are far outweighed by the huge security problems caused by "insecure by default" model. And it wouldn't be hard to implement secure templating - just make a subclass of String meant for raw html and make default String and anything wichh to_ses get HTML-escaped.

Both HAML and RHTML are very powerful as templating languages. Ruby is simply very well suited for the job. Completely unlike Python and Java which needs hundreds of lame templating languages. With a few partials, helpers and RJS snippets it's usually hard to imagine a shorter and more natural way of writing it all.

One more nice thing about ERB - it can be used pretty much everywhere, like in database.yml for switching database adapter depending on whether it's JRuby or matz's Ruby, or in SQL snippets meant for initializing database. Maybe that's not a huge deal but there's not other language where it's so natural to do.


Controllers are basically small bags of actions which actually do stuff. Separation between controllers and views has one huge wart - flash. It doesn't clearly belong in either. And if you want things like markup and links inside flash messages - a perfectly reasonable thing to do - it gets uglier that Perl on a bad day. I'm not sure what's the right way to do it, flash partials maybe ? Or full set of link helpers available inside controller.

Functional testing reuses controller objects without cleaning out their instance variables between requests. That's just wrong. It also reuses request and response objects for no particular reason. Oh, and it silently ignores 403s, flash[:error], doesn't follow redirects, and relies on cross-site request forgery to get any testing done - if forms include a security token in hidden field you cannot test by directly posting, you must use the actual form ! This is probably the most broken part of Ruby on Rails.

A good functional test would look something like that:
def test_that_edit_respects_item_ownershit
get :edit, :id => your_item
form.fill_and_sumbit :x => "Foo", :y => "Bar"
assert_raises Error403 {
get :edit, :id => somebody_elses_item
form.fill_and_sumbit :x => "Foo", :y => "Bar"
assert_equal "This item belongs to someone else.", flash[:error]

but it's a long way to get anywhere near that point. form-test-helper is probably a good start.


Models in Ruby on Rails are based on an idea that you can either have a very high way view or go raw SQL but nothing in between.

Raw SQL wouldn't be that bad if they at least handled security somehow (execute accepting "%" would be a good start), strings returned from SQL were converted to Ruby objects (surprisingly timestamps get returned as Ruby objects in some databases), and results of execute supported map method. Or wait - it would be bad, it's SQL after all. Why are we still using RDBMSes in 2007, weren't they supposed to die together with Fortran or something ?

Good thing about models is how easy it is to move code between controllers and models. This barrier is much more permeable than controller-view barrier, resulting in easier refactoring and code looking better. Controller-view refactoring is usually much harder.

There's a lot of stuff that doesn't clearly fit in MVC like extensions to core classes, objects that are not backed by database, helpers and so on. It would be nice if it there was a place for putting tests of it.


There are two ways of doing routes, both bad. One is the old way as seen on screencasts. It ends with paths like /posts/123/destroy which are then fetched by web spiders deleting all your database. The new way is trying to make every controller fit REST model, so you end with DELETE /post_sharabilities/456 or something as stupid. If there is a good way of routing stuff I haven't seen it yet.

A good thing is that you can pretty much ignore it, use simple routes and filter out GETs in the controller. Controller filters are simply awesome, model filters are pretty good too. You can use them to handle things like authorization. One thing they unfortunately cannot handle is data integrity. Unfortunately Active Record hooks are too weak to handle things like ensuring that each person has exactly one primary email address. Why cannot RDBMSes just die ?


The first annoying thing about Ruby on Rails testing are fixtures. Each test runs inside a transaction so why are they wiped out and reapplied once for each test class ? And they really do not scale. There must be a better solution but I'm not sure what is it. One thing is certain - while mocha is great mocks aren't it, as often hundreds of objects must exist at the same time for testing to be useful.

Permeability of model-controller barrier also means that many things are only tested in controller tests (called "functional" tests in Ruby on Rals but I'm not sure if I like this abuse of terminology). The result - 90%+ in rcov report while half of the model methods are not tested in isolation.

Rake and Capistrano

Rake is simply awesome. It is to other building tools what Rails is to J2EE. Capistrano on the other hand, I have no idea why wasn't simply implemented on top of rake. Maybe it's time to take a look at Vlad the Deployer.


Another nice thing about Rails is great hackability. Most behaviors can be easily hacked and most hacks can be easily extracted to plugins. A few things like schema dumper weren't that easily extensible but overall most of the stuff I wanted to hack was very simple to hack. It's also a great thing how 30 independently developed plugins each monkeypatching some Ruby or Rails behavior can work together with almost no conflicts.

Documentaton and console

Code grepping is usually the best documentation. was sometimes helpful but not always. Trying things out in script/console was usually enough to explore and debug model. Unfortunately it doesn't work with controllers as path helpers and controller action runners are simply not defined there, so I cannot jump from a failing test to console to find out what's going on.

Other stuff

TextMate is great. Usually I hate every program I spend more than half an hour with. In this case I only somewhat dislike some parts of it, what probably means less fussy programmers will just love it ;-)