Bug of the day

Completely bad code follows, beware.

Silent error in Ruby 1.8.7:

x = [:a, :b]
=> [:a, :b]

=> nil

=> [:a, :b]

Explicit error (resulting in a failing test) in Ruby 1.9.2:

x = [:a, :b]
=> [:a, :b]

TypeError: can't convert Symbol into Integer

Just yet another incompatibility, but for the better!

Run guard-jasmine-headless-webkit without X server

You write specs for your javascript, right? If not, you really should.

jasmine-headless-webkit really helps with that. guard-jasmine-headless-webkit makes it all even more enjoyable, although there’s one caveat – it’s not so easy to set it all up.

There is a great guide for that, but it lacks some important details on running guard-jasmine-headless-webkit without graphical interface (X server).

Assuming you already have Xvfb installed, execute this command to run Xvfb in the background:

Xvfb :0 -screen 0 1024x768x24 > /dev/null 2>&1 &

And then you need to setup the DISPLAY shell variable in order for guard-jasmine-headless-webkit to automatically connect to our virtual frame buffer. Here’s the excerpt from my .bash_profile (it first checks if there is Xvfb running on display :0 and only then sets the DISPLAY variable):

xdpyinfo -display :0 &>/dev/null && export DISPLAY=:0

Hash to HTML (hash2html) in Ruby

I needed to output a Hash as a nested HTML structure. Googling didn’t find any satisfactory results, so I decided to roll my own. UL/LI tags seemed like the best choice. It was a nice exercise in recursion.

The result is a function, which outputs a nicely indented HTML. Note, however, that it’s a very basic solution. It doesn’t cope well with anything other than Strings and Numbers (unless your objects support a nice to_s method).

# Prints nested Hash as a nested <ul> and <li> tags
# - keys are wrapped in <strong> tags
# - values are wrapped in <span> tags
def HashToHTML(hash, opts = {})
  return if !hash.is_a?(Hash)

  indent_level = opts.fetch(:indent_level) { 0 }

  out = " " * indent_level + "<ul>\n"

  hash.each do |key, value|
    out += " " * (indent_level + 2) + "<li><strong>#{key}:</strong>"

    if value.is_a?(Hash)
      out += "\n" + HashToHTML(value, :indent_level => indent_level + 2) + " " * (indent_level + 2) + "</li>\n"
      out += " <span>#{value}</span></li>\n"

  out += " " * indent_level + "</ul>\n"

Who knows, maybe someone somewhere finds it useful.

Update: much more concise solution by Piotr Szotkowski.

hookup is the shit!

This is simply amazing:

$ g pull
Already up-to-date.

$ g co edge
Switched to branch 'edge'
==  AddFileTypeToSong: migrating ==============================================
-- add_column(:songs, :file_type, :string)
   -> 0.0048s
==  AddFileTypeToSong: migrated (0.1380s) =====================================

$ g rebase master
Current branch edge is up to date.

$ g co master
Switched to branch 'master'
==  AddFileTypeToSong: reverting ==============================================
-- remove_column(:songs, :file_type)
   -> 0.1674s
==  AddFileTypeToSong: reverted (0.1679s) =========================

Oh, and it will bundle automatically for you as well, so don’t hesitate and hookup your Rails project!

Dual Core systems

Back at the day I used to recommend dual core processors to my friends precisely becase of one reason:

Since there are not that many applications at the moment utilizing the power of two cores, the best use case for them is this: when your application hangs up it sometimes eats up to 100% of your CPU and you you cannot even move your mouse or click anywhere simply because there is not enough processing power left. Now with two cores, when your application hangs up like that, you still have that second core sitting idle in the background and you can quickly bring up task manager and kill the misbehaving app.

Nowadays, when by far the most used and abused application is the web browser, and when each tab is its own process, from time to time I see all of my cores – two, to be exact – being fully utilized up to a point that typing or switching to another application becomes almost impossible. Even mouse movement becomes shattered (and I’m on a Core 2 Duo 2.53GHz). I feel like being back at the single core times. Four cores might behave a little better, but maybe eight is the target to reach? I’m worried that the browser will just eat them up, no matter how many you’ll have.

Applications utilizing multiple cores are actually very appreciated, it’s just too bad, that this model has some drawbacks.

On Heroku

While Heroku is nice and all, it suffers from the same disease as every other hosted-for-you solution:

$ git push heroku
-----> Gemfile detected, running Bundler version 1.0.7

$ bundle --version
Bundler version 1.0.10

It’s a whole three patch versions behind! Now I don’t really know (and maybe don’t even really want to know) what has changed between .7 and .10, but I can easily imagine things braking precisely because those minor inconsistencies in Bundler versions.

And sure, I could downgrade to .7, but to do that just because of Heroku? Thank you, but no. I want to ride the latest.