When you tell rbenv to install a Ruby it does not know about, you will get an error message.

$ rbenv install 2.1.2
ruby-build: definition not found: 2.1.2

You can list all available versions with `rbenv install --list'.

If the version you're looking for is not present, first try upgrading
ruby-build. If it's still missing, open a request on the ruby-build
issue tracker: https://github.com/sstephenson/ruby-build/issues

(Fun fact: Recent versions of ruby-build will give you a more helpful error message which...

MenuetOS is an Operating System in development for the PC written entirely in 32/64 bit assembly language. Menuet64 is released under License and Menuet32 under GPL. Menuet supports 32/64 bit x86 assembly programming for smaller, faster and less resource hungry applications.

• Fits on a single floppy, boots also from CD and USB drives
• Responsive GUI with resolutions up to 1920x1080, 16 million colours
• Free-form, transparent and skinnable application windows, drag'n drop
• SMP multiprocessor support with currently up to 8 cpus
• IDE: E...

So you have a restangular collection and you want to remove an element from it, after you've successfully deleted it from the server.

The README suggests to say something like $scope.users = _.without($scope.users, user). While that works at first glance (the element is no longer in your collection), it will break horribly when you want to use restangular's attributes on that collection.

This...

If you regularly get ActionView::MissingTemplate exceptions, maybe some bot visits your site requesting silly formats like:

http://www.rails-app.com/makandra.html-username-2000 # => Rails tries to retrieve 'makandra' with format 'html-username-2000'

Just restrict accepted format parameters for the whole application like this:

class ApplicationController < ActionController::Base

  before_filter :refuse_silly_formats

  private

  def refuse_silly_formats
    acceptable_formats = %w[html xml pdf]

    if par...

better_errors is an awesome gem for enhanced error pages in development, featuring a live-REPL for some light debugging.

To debug the exception you got on an AJAX-Request, visit /__better_errors on your app's root path (e.g. http://localhost:3000/__better_errors). It shows the error page for the last exception that occurred, even when it has been triggered by an AJAX request.

Your development machine is usually on a very good network connection.
To test how your application behaves on a slow network (e.g. mobile), you can simulate limited bandwidth.

Chrome

• Open the dev tools (Ctrl+Shift+I or F12) and switch to the "Network" tab
• In the row below the dev tool tabs, there's a throttling dropdown which reads "Online" by default.
• Inside the dropdown, you will find a few presets and an option to add your own download/upload/latency settings.

Firefox

• Open the dev tools (Ctrl+Shift+I or F12) and switc...

Batman is an alternative Javascript MVC with a similar flavor as AngularJS, but a lot less features and geared towards Ruby on Rails.

The attached link leads to a tutorial for a small blog written with Rails / Batman.js.

I'm collecting other Batman.js resources in my bookmarks.

Development environment setup

Rails Composer

Basically a comprehensive Rails Template. Prepares your development environment and lets you select web server, template engine, unit and integration testing frameworks and more.

Generate an app in minutes using an application template. With all the options you want!

Code generators

Rails Bricks

A command line wizard. Once you get it running, it creates sleek applications.

RailsBricks enables you to cre...

Browsers usually cache favicons. If you update the favicon of your web site and want all visitors to see the new icon, you need to give the icon a different URL. You will not have this issue if you cache your assets properly, which appends a fingerprint to your image URL (like favicon.ico?432423432):

<link href="<%= image_path('favicon.ico') %>" rel="icon" type="image/vnd.microsoft.icon">

Introducing Trailer from HouseTrip, a simple menu bar app that helps you manage your GitHub pull requests. It’s one feature we felt was lacking from our workflow!

When you do something like this in your code:

def var_value
  @var ||= some_expensive_calculation
end

Be aware that it will run some_expensive_calculation every time you call var_value if some_expensive_calculation returns nil.

This illustrates the problem:

def some_expensive_calculation
  puts "i am off shopping bits!"
  @some_expensive_calculations_result
end

When you set @some_expensive_calculations_result to nil, ||= runs some_expensive_calculation every time....

TLDR: This card explains which threads and processes interact with each other when you run a Selenium test with Capybara. This will help you understand "impossible" behavior of your tests.

When you run a Rack::Test (non-Javascript) test with Capybara, there is a single process in play. It runs both your test script and the server responding to the user interactions scripted by your test.

A Selenium (Javascript) test has a lot more moving parts:

1. One process runs your test script. This is the process you...

CarrierWave attachments have two distinct methods #url and #path which appear to behave the same:

document.file.url   # => /storage/documents/4/letter.doc
document.file.path  # => /storage/documents/4/letter.doc

However, starting with CarrierWave 0.9, #url will properly escape high-ASCII characters:

document.file.url   # => /storage/documents/4/h%C3%BCte.doc
document.file.path  # => /storage/documents/4/hüte.doc

So always use #url if you mean an actual URL (e.g. to display an <img>). But use #path if y...

Rack::Attack is a rack middleware to protect your web app from bad clients. It allows whitelisting, blacklisting, throttling, and tracking based on arbitrary properties of the request.

When I upgraded from 0.5.4 PDFKit deadlocked or crashed when an ApplicationController::RouteError occured. If this error happens only because of a broken image link you probably still wan't the page to render and get a PDF with a "missing image placeholder" instead.

I don't know yet in which version (0.5.2, 0.5.3 or 0.5.4) the bug was built in. At the moment I'm doing fine with 0.5.1 and I didn't evaluate any other versions yet.

I will update this card as soon as I know further information (State 4th Nov. 2013).

Ubuntu 12.04 LTS x64, Ruby 1.8.7, Rails 2.13, PDFKit 0.5.4, Phusion Passenger Apache 2

I ran into this, when I started using passenger to deal with the Single Thread Issue which caused my webrick to deadlock when an ActionController::RoutingError (No route matches "...") occurred.

These steps brought me a little further

(1) assert dependencies are installed

 sudo aptitude install openssl build-essential xorg libssl-dev

(2) only for 64bits OS Run one by one the follo...

Weighttp is threaded and might exhaust resources of an application better than ApacheBench or httperf.

You need libev installed.

sudo apt-get install libev-dev

./waf configure
sudo ./waf install

Rails has always included a scaffold script that generates a default controller implementation for you. Unfortunately that generated controller is unnecessarily verbose.

When we take over Rails projects from other teams, we often find that controllers are the unloved child, where annoying glue code has been paved over and over again, negotiating between request and model using implicit and convoluted protocols.

We prefer a different approach. We believe that among all the classes in a Rails project, controllers are some of the hardest to...

If you need to test interaction with a remote API, check out the VCR gem as an alternative to Webmock or stubbing hell.

The idea behind VCR is that is performs real HTTP requests and logs the interaction in a .yml file. When you run the test again, requests and responses are stubbed from the log and the test can run offline.

It's a great way to mock network requests to an external service without going through the pain of log...

So you client has asked you to implement a row of buttons to like the URL on Facebook, Twitter and Google+. Here are some things you should know about this.

0. Security considerations

Each "like" button is implemented by including a Javascript on your site. This means you are running fucking remote code on your page. You are giving Facebook, Twitter and Google+ full permission to e. g. copy user cookies. Check with your client if she is cool with that. Also note that if you're site is suggesting security by operating under HTTPS ...