Ruby: Using the pry debugger in projects with older Ruby versions

In case you want to use pry with an older version of Ruby, you can try the following configurations.

Ruby 1.8.7

Your pry version must not be greater than 0.9.10.

gem 'pry', '=0.9.10'
gem 'ruby-debug'
gem "ruby-debug-pry", :require => "ruby-debug/pry"
gem 'pry-nav'
gem 'ruby18_source_location'

Ruby 1.9.3

Your pry version must not be greater than 0.9.9.

gem 'debugger', '=1.1.4'
gem 'pry-debugger', '=0.2.0'
gem 'pry', '=0.9.9'

Known errors

No source for ruby-1.9.3-p551 p...

Linked content

The ultimate guide to Ruby timeouts

An unresponsive service can be worse than a down one. It can tie up your entire system if not handled properly. All network requests should have a timeout.

Here’s how to add timeouts for popular Ruby gems. All have been tested. You should avoid Ruby’s Timeout module. The default is no timeout, unless otherwise specified. Enjoy!


Webpacker: Configuring browser compatibility

Webpacker uses Babel and Webpack to transpile modern JavaScript down to EcmaScript 5. Depending on what browser a project needs to support, the final Webpack output needs to be different. E.g. when we need to support IE11 we can rely on fewer JavaScript features. Hence our output will be more verbose than when we only need support modern browsers.

Rails 5.1+ projects often use Webpacker to preconfigure the Webpack pipeline for us. The default configuration works something like this:

  1. Webpack checks w...

CarrierWave: How to generate versions with different file extensions

We use CarrierWave in many of our projects to store and serve files of various formats - mostly images. A common use case of CarrierWave's DSL is to "process" the original file in order to create multiple "versions", for example different resolutions of the same image.

Now we could go one step further: What if we want to create versions that have a different file extension than the original file? For example, let's assume we'd like to create a ve...


Ruby: Referencing global variables with the built-in English library

With Ruby's build-in library English you can reference global variables with an english name. This makes you code easier to read and is also suggested by Rubocop's Style/GlobalVars cop.

Example before:

if 'foo' =~ /foo/
  puts $~[1] # => foo

Example after:

if 'foo' =~ /foo/
  puts $LAST_MATCH_INFO[1] # => foo

Require pitfall in Rails

The English library is not loaded by default in Rails. S...


How Rails and MySQL are handling time zones

When working with times and dates in Rails applications, you need to deal with the following problem:

  • In Rails, Time objects have a time zone. You can get the zone name by doing
  • This zone is considered when doing time calculations, e.g. 10 AM CEST minus 8 AM UTC is zero.
  • A datetime in MySQL does not have a zone. It just stores the literal string "2010-05-01 12:00:00".
  • That means that Rails must make assumptions about timestamps loaded from and written to MySQL.

Rails has two completely different modes ...

whenever: Installing cron jobs only for a given Rails environment or Capistrano stage

We use the whenever gem to automatically update the crontab of the servers we deploy to. By default, whenever will update all servers with a matching role (we use the :cron role ).

This card describes how to install some tasks only for a given Rails environment or for a given Capistrano stage.

Installing jobs only for a given Rails environment

In yo...


How to update a single gem conservatively

The problem

Calling bundle update GEMNAME will update a lot more gems than you think. E.g. when you do this:

bundle update cucumber-rails

... you might think this will only update cucumber-rails. But it actually updates cucumber-rails and all of its dependencies. This will explode in your face when one of these dependencies release a new version with breaking API changes. Which is all the time.

In the example above updating cucumber-rails will give you Capybara 2.0 (because capybara is a dependency of `cucumber-rail...

Linked contentAuto-destruct in 15 days

Updated: How to discard a surrounding Bundler environment

Updated card to use Bundler.with_original_env which is what you actually always wanted.

Also added a note on what with_unbundled_env (or with_clean_env on legacy versions) does.

Auto-destruct in 4 days

Geordi 3 released

We released two new versions of Geordi. For projects with Ruby 1.8.7 or 1.9.3 you now have to run gem install geordi -v '~>2' to get a compatible version.

Geordi 2.11.0

Compatible changes

  • Added the possibility to change the Rails root for the capistrano config via the environment variable RAILS_ROOT. This allows you as a gem developer to run a command like RAILS_ROOT=~/Projects/my-blog geordi console staging whereas geordi uses the capistrano config from my-blog. Otherwise you would need to follow the instructions of [th...

Rubygems: Installing the last version of rubygems that has no rubyforge_project deprecation warning

You can install rubygems 3.0.8 (released on February 18, 2020) to keep all the Gem::Specification#rubyforge_project deprecation warnings away from your development log. With Rubygems >= 3.1 this deprecation warning was introduced. While maintaining older projects this could get quite annoying and the fix below might okey, for newer projects the right ways is to upgrade the gems.

gem update --system 3.0.8

Example message:

NOTE: Gem::Specification#rubyforge_project= is deprecated with no replacement. It will be removed o...

How to: Run bundle install in parallel

You can run bundle install in parallel. This might be helpful for development, where you often install many new gems when switching between projects.

  1. Find out the number of processors you have:
  1. Set the config in your ~/.bundle/config globally (replace 8 with your number of proccessors):
bundle config jobs 8

Note: If you suspect parallel execution for bundling issues, you can try serially with bundle install --jobs 1.

Linked content

Five years of "Today I Learned" from Josh Branchaud

The linked GitHub repository is a bit like our "dev" cards deck, but groomed from a single person (Josh Branchaud). It includes an extensive list of over 900 TILs on many topics that might be interesting for most of us. (e.g. Ruby, Rails, Git, Unix..)


Here is an excerpt of all the Ruby TILs that were new to me. I encourage you to take your time to skim over the original list as well!

Rails: Concurrent requests in development and tests

With puma you can have concurrent requests. There are two concepts on how Puma can handle two incoming requests: Workers and Threads.


Puma can have multiple workers. Each worker is a process fork from puma and therefore a very heavy instance and can have multiple threads, that handle the incoming requests.

Example: A Puma server with 2 workers and 1 thread each can handle 2 request in parallel. A third request has to wait until the thread of one of the workers is free.


Rails is thread-safe since version 4 (n...

How to use Simplecov to find untested code in a Rails project with RSpec and Cucumber

Simplecov is a code coverage tool. This helps you to find out which parts of your application are not tested.

Integrating this in a rails project with rspec, cucumber and parallel_tests is easy.

  1. Add it to your Gemfile and bundle

    group :test do
      gem 'simplecov', require: false
  2. Add a .simplecov file in your project root:

    SimpleCov.start 'rails' do
      # any custom configs like groups and filters can be here at a central place



How to use a local gem in your Gemfile

You can use local copies of gems in your Gemfile like this:

gem 'spreewald', :path => '~/gems/spreewald'

As soon as you have bundled your project with the local copy of the gem, all code changes in the copy will be available on your project. So you can for example set a debugger or add console output in the gem and use it from your project.
If you checked out the gem with your versioning tool, you can easily reset your changes afterwards or make a pull request for the gem if you improved it.

Don't commit a Gemfile with local pat...

Video transcoding: Web and native playback overview (April 2020)


Embedding videos on a website is very easy, add a <video> tag to your source code and it just works. Most of the time.

The thing is: Both the operating system and Browser of your client must support the container and codecs of your video. To ensure playback on every device, you have to transcode your videos to one or more versions of which they are supported by every device out there.

In this card, I'll explore the available audio and video standards we have right now. The goal is to built a pipeline that transcodes unknown ...

Linked contentRepeats

Writing a README for a project

Rails applications and ruby gems should have a README that gives the reader a quick overview of the project. Its size will vary as projects differ in complexity, but there should always be some introductory prose for a developer to read when starting on it.


That's already the main purpose of a project README: Give a new developer a quick overview of the project. In sketching this outline, the README should notify the reader of any peculiarity he needs to know of.

Remember that in a few months, you'll be a kind of "new ...

This website uses cookies to improve usability and analyze traffic.
Accept or learn more