I’ve been debugging this PHP application at work that was written by a 3rd-party. After cleaning up the XSS and SQL injection vulnerabilities in it, we found a new bug. It’s minor, yet important.

While tracking down the offending line, I needed to deploy various revisions of the website. It turns out that it’s really easy to do this with Capistrano:

$ cap -S revision=3f30b6de3c55a8347e5f3de3b43193591e6c7322 beta deploy

One thing I noticed was the need to provide the full SHA-1 object name (AKA revision ID, commit ID). Normally with Git, you can provide the first few characters of a commit ID. For example:

$ git checkout 3f30b6de

instead of

$ git checkout 3f30b6de3c55a8347e5f3de3b43193591e6c7322

I guess Capistrano’s a bit more picky!

Sometimes, there’re restrictions on what patterns you can use. I wanted to change a regex for validating passwords. Originally, it allowed letters, numbers, and a seemingly random collection of special characters. How lame is this?:

^[A-Za-z0-9]{1}[A-Za-z0-9_\\.\\!\@\#\-]{0,255}$

Not only are the allowed special characters arbitrary, but they’re escaping characters in a character class, and using “{1}”.

I tried changing the regex to this:

^[[:print:]]{0,255}$

Unfortunately, that wasn’t considered “valid” by the system in question. Luckily, there’s a fairly concise alternative:

^[\x20-\x7E]{0,255}$

If you find a system that lacks support for POSIX character classes, check out this Wikipedia article.

All your app needs is the usual Rackup config file (config.ru) in the app’s root directory, and the directory public/ .

There’s one caveat, though: if you have a file named environment.rb , do not put it in config/ .

If mod_rails finds config/environment.rb , it’ll think your app runs on Rails:

By using Backports, and not worrying so much.

First, setup your box to be able to install backports of packages. Next, uninstall any Ruby-related packages. Yeah, that’s right. Do you know why? Because, if you’re running Etch, you’re using Ruby 1.8.5! Egad! That’s almost medieval. Make sure to uninstall irb and rdoc, too.

Now it’s time to install shinier versions…1.8.7, to be exact:

$ sudo aptitude install -t etch-backports libruby1.8 ruby1.8 rdoc1.8 irb1.8

All of that should be on one line.

There you have it. Now you’ve got Ruby 1.8.7 on Debian Stable (AKA “Etch”). Ruby’s not complete without RubyGems, though. Download the latest version to /usr/src/ , and extract it:

$ cd /usr/src/$ wget http://rubyforge.org/frs/download.php/45905/rubygems-1.3.1.tgz$ tar zxf rubygems-1.3.1.tgz

Then run the setup utility:

$ cd rubygems-1.3.1/$ sudo ruby setup.rb

Let’s do one last thing to make life easier. The RubyGems setup script installed the “gem” command as /usr/bin/gem1.8 . I don’t want to have to type that “1.8″ every time.

$ cd /usr/local/bin/$ sudo ln -v -s /usr/bin/gem1.8 gem

There. Now we can run “gem” like the rest of the world.

Easy? Yar.

For example, let’s rebuild that Stegosaurus class from a previous post:

class Stegosaurus < ActiveRecord::Base  attr_accessible :tail_spikes, :back_plates

  validates_numericality_of :tail_spikes,      nly_integer             => true,    :greater_than_or_equal_to => 0

  validates_numericality_of :back_plates,      nly_integer             => true,    :greater_than_or_equal_to => 0end

With that, if we created a new Stegosaurus and didn’t specify any attributes, not only would it have no tail spikes or back plates, but the model instance wouldn’t be valid.

To fix that, all we need to do is add two lines:

class Stegosaurus < ActiveRecord::Base  attr_accessible :tail_spikes, :back_plates

  default :tail_spikes => 4  default :back_plates => 6

  validates_numericality_of :tail_spikes,      nly_integer             => true,    :greater_than_or_equal_to => 0

  validates_numericality_of :back_plates,      nly_integer             => true,    :greater_than_or_equal_to => 0end

And voila, new Stegosaurus objects will automatically have 4 tail spikes and 6 back plates:

>> s = Stegosaurus.new=> #<Stegosaurus tail_spikes: 4, back_plates: 6>>> ?> s.tail_spikes=> 4>> s.back_plates=> 6

However, if used improperly, this can lead to several hours of pounding your head on your desk. Note that that the default values we used above, 4 and 6, are immutable objects. You can’t change them. You can perform operations on them, such as addition (4 + 1), but that never changes the object.

Say we want our Stegosaurus class to have an array specifying its diet that defaults to “fern” and “cycad”:

class Stegosaurus < ActiveRecord::Base  attr_accessible :tail_spikes, :back_plates, :diet

  default :tail_spikes => 4  default :back_plates => 6  default :diet => %w(fern cycad)

  validates_numericality_of :tail_spikes,      nly_integer             => true,    :greater_than_or_equal_to => 0

  validates_numericality_of :back_plates,      nly_integer             => true,    :greater_than_or_equal_to => 0end

That looks right. But watch this:

=> charles = Stegosaurus.new=> #<Stegosaurus tail_spikes: 4, back_plates: 6, diet: ["fern", "cycad"]>>> ?> arnold = Stegosaurus.new=> #<Stegosaurus tail_spikes: 4, back_plates: 6, diet: ["fern", "cycad"]>>> ?> charles.diet < < 'moss'=> ["fern", "cycad", "moss"]>> ?> arnold.diet=> ["fern", "cycad", "moss"]

We didn’t mean to do that…Arnold doesn’t want to eat moss!

At the moment, when the Stegosaurus class is initialised, it creates one Array for the default “diet” attribute of all future Stegosaurus objects. In other words, Charles’ and Arnolds’ “diet” attributes were references to the same object:

>> charles.diet.object_id=> 19103090>> ?> arnold.diet.object_id=> 19103090

How do we fix that? We tell the Stegosaurus class to create a new Array for each model instance. Simply change this:

default :diet => %w(fern cycad)

to this:

default :diet => Proc.new { %w(fern cycad) }

Now each time we create a new Stegosaurus, that Proc will fire, and create a new “diet” Array:

=> charles = Stegosaurus.new=> #<Stegosaurus tail_spikes: 4, back_plates: 6, diet: ["fern", "cycad"]>>> ?> arnold = Stegosaurus.new=> #<Stegosaurus tail_spikes: 4, back_plates: 6, diet: ["fern", "cycad"]>>> ?> charles.diet < < 'moss'=> ["fern", "cycad", "moss"]>> ?> arnold.diet=> ["fern", "cycad"]

I highly recommend giving active_record_defaults a try. It’s very handy, and very easy to use.

And by the way, yes, I was bitten by this problem. Why else would I be writing about it! Can you guess how I discovered it, though? … My tests picked it up!

RSpec is a really awesome testing framework. By “awesome”, I mean that it:

• makes it easy to write tests;
• makes your tests easy to read;
• gives you an easy development path to follow.

It accomplishes this by following behaviour-driven development (BDD). If you’re not a keener, don’t bother following that link. Just read on for the stegosaurus.

With BDD, you write specs that describe your application’s behaviour in terms of what it should and shouldn’t do.

Let’s write an app to mimic one of my favourite dinosaurs. And while we’re at it, we’ll do some testing. But first, install RSpec:

sudo gem install rspec

Stegosauruses are known for 2 things. Let’s start with those awesome tail spikes:

class Stegosaurus  attr_accessor :tail_spikesend

That’s pretty simple. So how do we spec this? We start off by describing what we want our application to do. In this case, we should be able to grab the “tail_spikes” attribute:

require 'stegosaurus'

describe Stegosaurus doit 'should have tail spikes' do  steggie = Stegosaurus.new

  steggie.should respond_to :tail_spikes  steggie.should respond_to :tail_spikes=endend

Run the spec, and we’re off to the races!

$ spec stegosaurus_spec.rb.

Finished in 0.015328 seconds

1 example, 0 failures

We should also spec setting the number of tail spikes, so let’s update the spec:

require 'stegosaurus'

describe Stegosaurus doit 'should have tail spikes' do  steggie = Stegosaurus.new

  steggie.should respond_to :tail_spikes  steggie.should respond_to :tail_spikes=

  steggie.tail_spikes = 4  steggie.tail_spikes.should equal 4endend

That’s one of the most readable and easy-to-understand tests you’ve ever seen, eh?

Stegosauruses are also known for the huge plates on their backs:

class Stegosaurusattr_accessor :tail_spikesattr_accessor :platesend

The spec should be pretty obvious:

require 'stegosaurus'

describe Stegosaurus doit 'should have tail spikes' do  steggie = Stegosaurus.new

  steggie.should respond_to :tail_spikes  steggie.should respond_to :tail_spikes=

  steggie.tail_spikes = 4  steggie.tail_spikes.should equal 4end

it 'should have plates' do  steggie = Stegosaurus.new

  steggie.should respond_to :plates  steggie.should respond_to :plates=

  steggie.plates = 12  steggie.plates.should equal 12endend

Notice, though, that we’re beginning to repeat ourselves. In both of those examples (#it blocks), we create a new Stegosaurus. Let’s tidy that up a bit:

require 'stegosaurus'

describe Stegosaurus dobefore :each do  @steggie = Stegosaurus.newend

it 'should have tail spikes' do  @steggie.should respond_to :tail_spikes  @steggie.should respond_to :tail_spikes=

  @steggie.tail_spikes = 4  @steggie.tail_spikes.should equal 4end

it 'should have plates' do  @steggie.should respond_to :plates  @steggie.should respond_to :plates=

  @steggie.plates = 12  @steggie.plates.should equal 12endend

What we did there is tell RSpec to create a new Stegosaurus before each example is run. To make the stegosaurus available to the examples, it simply needs to be an instance variable.

When running your specs, there are a few different ways to format the output. I tend to use the default and “specdoc” formats. Currently, our spec’s output looks like this:

$ spec stegosaurus_spec.rb..

Finished in 0.01591 seconds

2 examples, 0 failures

But we can also tell RSpec to spit out a summary of our specs:

$ spec stegosaurus_spec.rb --format specdoc

Stegosaurus- should have tail spikes- should have plates

Finished in 0.057443 seconds

2 examples, 0 failures

Our Stegosaurus class is feeling a bit weird, though..technically, we can set the “tail_spikes” and “plates” attributes to any object:

$ irb>> require 'stegosaurus'=> true>>?> steggie = Stegosaurus.new=> #<Stegosaurus:0x602afc>>>?> steggie.tail_spikes = "we don't want to be able to do this!"=> "we don't want to be able to do this!"

So we need to restrict those two attributes to integers:

class Stegosaurusattr_reader :tail_spikesattr_reader :plates

def tail_spikes=(number_of_tail_spikes)  raise ArgumentError, 'The first argument (number_of_tail_spikes) must be a Fixnum.' unless number_of_tail_spikes.is_a? Fixnum

  @tail_spikes = number_of_tail_spikesend

def plates=(number_of_plates)  raise ArgumentError, 'The first argument (number_of_plates) must be a Fixnum.' unless number_of_plates.is_a? Fixnum

  @plates = number_of_platesendend

With that done, what do we need to change in our specs? We need to spec the behaviour of the 2 new setter methods:

require 'stegosaurus'

describe Stegosaurus dobefore :each do  @steggie = Stegosaurus.newend

describe '"tail_spikes" attribute' do  it 'can only be set to an integer' do    Proc.new {      @steggie.tail_spikes = 'asdf'      }.should raise_error ArgumentError, 'The first argument (number_of_tail_spikes) must be a Fixnum.'

    @steggie.tail_spikes = 4    @steggie.tail_spikes.should equal 4  endend

describe '"plates" attribute' do  it 'can only be set to an integer' do    Proc.new {      @steggie.plates = 'asdf'      }.should raise_error ArgumentError, 'The first argument (number_of_plates) must be a Fixnum.'

    @steggie.plates = 12    @steggie.plates.should equal 12  endendend

Most of that is pretty self-explanatory. However, notice that we’ve just nested #describe inside of the original #describe…twice! We do this because it makes are specs read more fluidly, and it groups examples (#it blocks) together. And inside these inner-#describes, we can do anything we talked about earlier, like setup a before-block.

Let’s add one more attribute…a name:

class Stegosaurusattr_reader :tail_spikes, :plates, :name

def tail_spikes=(number_of_tail_spikes)  raise ArgumentError, 'The first argument (number_of_tail_spikes) must be a Fixnum.' unless number_of_tail_spikes.is_a? Fixnum

  @tail_spikes = number_of_tail_spikesend

def plates=(number_of_plates)  raise ArgumentError, 'The first argument (number_of_plates) must be a Fixnum.' unless number_of_plates.is_a? Fixnum

  @plates = number_of_platesend

def name=(name)  raise ArgumentError, 'The first argument (name) must be a String.' unless name.is_a? String

  @name = nameendend

And now the specs look like:

require 'stegosaurus'

describe Stegosaurus dobefore :each do  @steggie = Stegosaurus.newend

describe '"tail_spikes" attribute' do  it 'can only be set to an integer' do    Proc.new {      @steggie.tail_spikes = 'asdf'    }.should raise_error ArgumentError, 'The first argument (number_of_tail_spikes) must be a Fixnum.'

    @steggie.tail_spikes = 4    @steggie.tail_spikes.should equal 4  endend

describe '"plates" attribute' do  it 'can only be set to an integer' do    Proc.new {      @steggie.plates = 'asdf'    }.should raise_error ArgumentError, 'The first argument (number_of_plates) must be a Fixnum.'

    @steggie.plates = 12    @steggie.plates.should equal 12  endend

describe '"name" attribute' do  it 'can only be set to a string' do    Proc.new {      @steggie.name = ['not valid']    }.should raise_error ArgumentError, 'The first argument (name) must be a String.'

    @steggie.name = 'Rupert'    @steggie.name.should equal 'Rupert'  endendend

Let’s run that spec now:

$ spec stegosaurus_spec.rb..F

1)'Stegosaurus "name" attribute can only be set to a string' FAILEDexpected "Rupert", got "Rupert" (using .equal?)./stegosaurus_spec.rb:37:

Finished in 0.02225 seconds

3 examples, 1 failure

Hrmmm, that’s no good. But that’s a fairly useful error message, eh?…well, sort of. It’s telling us what it expected, and what it received. The thing is, it expected “Rupert” and got “Rupert”, so what’s going on? The problem lies in the fact that you can’t use #equal? to compare strings, and that’s exactly what we’re doing. If you don’t believe me, try it for yourself:

$ irb>> 'Rupert'.equal? 'Rupert'=> false

BTW, did you notice the “(using .equal?)” hint that RSpec gave us?

Enough banter. All we need to do is change this:

@steggie.name.should equal 'Rupert'

to this:

@steggie.name.should == 'Rupert'

Shall we view our specs in all their glory now?

$  spec stegosaurus_spec.rb --format specdoc

Stegosaurus "tail_spikes" attribute- can only be set to an integer

Stegosaurus "plates" attribute- can only be set to an integer

Stegosaurus "name" attribute- can only be set to a string

Finished in 0.018755 seconds

3 examples, 0 failures

Those’re the absolute basics of RSpec. If you’re thirsty for more, check out the RSpec website.

With that said, I’m joining in. I primarily use RSpec, so I’ll be focussing on that, but we’ll give Cucumber and other tools a go, and we’ll be starting with the basics.

So subscribe to our feeds, and stay tuned!

However, that’s not the case at all.

map.resources :photos, :as => 'images'

This allows you to request the “photos” resource using the word “images”. IE: http://localhost:3000/images/ would route to the “photos” controller.

On the other hand,

map.resources :photos, :controller => 'images'

This allows you to request the “images” resource using the word “photos”. IE: http://localhost:3000/photos/ would route to the “images” controller.

Simple? Yes. Subtle? Yes.

Vim formats them like this:

case foobarwhen 'something' # Do something.when 'another thing' # Do another thing.else # Do this if the above "when"s don't match.end

That indentation scheme doesn’t feel right to me. The “when” and “else” clauses are pretty much children of the “case” clause. In my opinion, “when” and “else” should be indented +1, like this:

case foobar when 'something'   # Do something. when 'another thing'   # Do another thing. else   # Do this if the above "when"s don't match.end

But now the code within each “when” and “else” is indented +2! That’s a lot of indentation.

I brought this up in #ruby-lang on Freenode. A couple of people agreed with me, a couple didn’t care, and the rest disagreed. There was one poignant comment though:

<quix> litage: why doesn't your reasoning for if/elsif apply to case/when?

I haven’t been able to answer that yet. quix’s reasoning is sound, but I can’t shake the dirtiness that I feel when indenting “when” and “else” to the same level as “case”. It just feels wrong…