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Updated: Install a gem without RI and RDdoc

Updated for recent Rubys: use --no-document

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Fix error: rails console No such file to load -- irb/encoding_aliases.rb (LoadError)

I got this error after upgrading Ruby from 2.4.5 to 2.6.4 when I opened the Rails console - rails server still worked.

Running via Spring preloader in process 14679
Loading development environment (Rails
Traceback (most recent call last): …/lib/ruby/gems/2.6.0/gems/spring-2.1.0/lib/spring/application.rb:175:in 'fork': No such file to load – irb/encoding_aliases.rb (LoadError) …/lib/ruby/gems/2.6.0/gems/spring-2.1.0/lib/spring/application.rb:175:in 'fork': undefined method 'reject!' for nil:NilClass (NoMethodError) …/li…


Linux: Shell script to easily update chromedriver

Updating Chromedriver is often a hassle: If you use chromium-chromedriver from the Ubuntu sources, it usually won't be updated when a new Chrome version is released. Manually downloading it from the official page is a very manual process. And I don't really want to use remote code like the "webdrives" gem because of paranoia.

Cry no more, for here is a tiny bash script that will download the latest chromedriver version and place it inside ~/bin. (If you use a different location, adjust accordingly).




Organize large I18n dictionary files in Rails 3+

If you're suffering from a huge de.yml or similiar file, cry no more. Rails lets you freely organize your dictionary files in config/locales.

My organization works like this:

  • config/locales/ modified Rails boilerplate
  • config/locales/ modified Faker boilerplate
  • config/locales/ model names, attribute names, assignable_value labels
  • `config/locales/…
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palkan/isolator: Detect non-atomic interactions within DB transactions

With this gem your transaction blocks raise an error when they have side effects that cannot be rolled back.

By default it checks whether you're connecting with HTTP, queuing a Sidekiq job or sending an e-mail within a transaction. You can add custom checks, too.

Found in this RubyGuides article.

Convert SCSS to SASS

The ruby sass gem also installs a command line tool to convert to and from SCSS. Use it for a directory of .scss-files like

sass-convert -R assets/stylesheets --from scss --to sass

Update a projects bundler version

We use bundler to maintain a projects gems. Unfortunately bundler v1 itself is incompatible with bundler v2.
You have two ways to update bundler on the server.

If you use our gem capistrano-opscomplete in your project, you can tell opscomplete to install the required bundler version:

Add the following line to deploy.rb. If you use different deployment targets, add the follwoing line to the specific target configuration file. (e.g `product…


Thread-safe collections in Ruby

When using threads, you must make your code thread-safe. This can be done by either locking (mutexes) all data shared between threads, or by only using immutable data structures. Ruby core classes like String or Array are not immutable.

There's several gems providing thread-safe collection classes in Ruby.


The concurrent-ruby gem provides thread-safe versions of Array and Hash:

sa = # supports standard forms
sh = Conc…

Take care of existing users when upgrading Clearance

When upgrading Clearance, pay attention whether the password hashing strategy might have changed. Old clearance versions (< 1.0) used SHA1-encrypted passwords by default. Current versions default to BCrypt.

If you simply upgrade without taking this into account, users will get a BCrypt::Errors::InvalidHash when trying to sign in. Your tests will not notice this, since they create new users for each scenario.

To fix it, you'll either have to force all users to reset their passwords, or you can allow old users to keep signing in with t…


When upgrading/downgrading RubyGems and Bundler on a server, you must clear bundled gems

On application servers, gems are usually bundled into the project directory, at a location shared across deployments.

This is usually shared/bundle inside your project's root directory, e.g. /var/www/your-project/shared/bundle/.
If you can't find that, take a look at current/.bundle/config and look for BUNDLE_PATH.

When you are changing the version of RubyGems or Bundler on a system where gems are installed this way, you must wipe that bundle directory in addition to the user and system gems or gems that are already ins…

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Choosing the right gems for your project

Adding a gem means you take over the liability towards the external code.


Based on "To gem, or not to gem":

  • Gem is really needed (prefer writing your own code for simple requirements without many edge cases)
  • Gem is tested well (coverage and quality)
  • Gem has a good code quality
  • Gem's licence fits to the project requirement
  • Try to avoid gems that do much more than your requireme…

Working with or without time zones in Rails applications

Rails supports time zones, but there are several pitfalls. Most importantly because and Time.current are completely different things and code from gems might use one or the other.

Especially configuring an application that cares only about one time zone is a bit tricky.

The following was tested on Rails 5.1 but should apply to Rails 4.2 as well.

Using only local time

Your life will be easier if your application does not need to support time zones. Disable them like this:

config.time_zone = 'Berlin' # Your local time…


RubyMine: Efficiently filtering results in the "Finder" overlay

RubyMine comes with a nice way to grep through your project's files: The finder (ctrl + shift + f). Don't be discouraged about the notice 100+ matches in n+ files if your searched keyword is too general or widely used in your project.


RubyMine comes with a few ways to narrow down the resulting list, don't hesitate to apply those filters to speed up your search. Your keybinding might vary based on your personal settings.

File mask (alt + k)

If you already know the file extension of your …


Webpack(er): A primer

webpack is a very powerful asset bundler written in node.js to bundle (ES6) JavaScript modules, stylesheets, images, and other assets for consumption in browsers.

Webpacker is a wrapper around webpack that handles integration with Rails.

This is a short introduction.


If you haven't already, you need to install node.js and Yarn.

Then, put

gem 'webpacker', '~> 4.x' # check if 4.x is still cu…


How to make RubyMine aware of Cucumber steps defined in gems

If your Ruby project includes a gem like Spreewald that comes with some external step definition, RubyMine does not know about them by default and will highlight the step as an undefined reference:


To link these external step definitions to RubyMine, add the corresponding gems to your RubyMine-Settings:

  • Go to Settings (ctrl + alt + s)
  • Go to Languages and Frameworks
  • Go to Cucumber
  • There, add your gem (e.g "spreewald") via the little "+" from the b…
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How to send HTTP requests using cURL

  • Reading a URL via GET:

  • Defining any HTTP method (like POST or PUT):

    curl -XPUT
  • Sending data with a request:

    curl -d"first_name=Bruce&last_name=Wayne"

    If you use -d and do not set an HTTP request method it automatically defaults to POST.

  • Performing basic authentication:

  • All together now:

    curl -XPUT -d"screen_name=batman"


How to define constants with traits

This is pretty much like defining subclasses through traits with the Modularity gem.

module MyConstantTrait
  as_trait do
    self::MY_CONSTANT = 'hello universe'

This would set MY_CONSTANT for any class using the trait.

Of course you can also use parameters (for logic or for setting values, like here):

module DoesValues
  as_trait do |*args|
    self::VALUES = args

class Foo
  include D...

How to: Fix json 1.8.3 with Ruby 2.5

The gem json fails to install for Ruby 2.5 if you use a version equal or below 1.8.3.

Run bundle update json --conservative to solve this issue.

The backtrace you will encounter looks like this:

Building native extensions. This could take a while…
ERROR: Error installing json:
ERROR: Failed to build gem native extension.

current directory: /home/user/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/json-1.8.3/ext/json/ext/generator /home/user/.rbenv/versions/2.5.3/bin/ruby -I /home/user/.rbenv/versions/2.5.3/lib/ruby/si...
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