Guide to localizing a Rails application

Localizing a non-trivial application can be a huge undertaking. This card will give you an overview over the many components that are affected.

When you are asked to give an estimate for the effort involved, go through the list below and check which points are covered by your requirements. Work with a developer who has done a full-app localization before and assign an hour estimate to each of these points.

Static text

  • Static strings and template text in app must be translated: Screens, mailer templates, PDF templates, helpe…
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Things you probably didn’t know you could do with Chrome’s Developer Console

Collection of useful tools in the Chrome JavaScript console.

Make the whole page editable
This is not special to Chrome, but still a clever thing:
Taking time
You can easily measure the time on the console with named timers:
console.time('myTime'); // Start timer
console.timeEnd('myTime'); // End timer and print the time
Reference previously inspected elements (from the Elements panel)
Variables $0, $1, … $n reference the nth-last inspected Element. $0 is the…
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Make your Rails console (and irb) output better readable

Pour color on your Rails console with awesome_print. Turn confusing long strings into formatted output. Have objects and classes laid out clearly whenever you need it.

Put gem 'awesome_print', :group => :development into your Gemfile. Now on the Rails console you have the command ap that will give you a colored, formatted output of whatever you pass it. See the example output of the User class below.

For customization visit the repository on Github.


Cucumber: How to find unused step definitions

Cucumber has an output format that prints step definitions only. You can use this to find unused ones:

  1. Temporarily add require_relative 'env' to the top of the first file in features/support. --dry-run makes Cucumber skip loading env.rb.
  2. Open a really wide terminal window.
  3. bundle exec cucumber --dry-run --format stepdefs | grep -B1 'NOT MATCHED' --no-group-separator | grep features/step_definitions

This will print all unused step definitions from your project – however, the result will include false positives. Step…

ActiveJob Inline can break the autoloading in development

We figured out, that ActiveJob Inline might lead to autoloading problems in development. The result was an exception when running an import script, which delivers async mails.

A copy of XXX has been removed from the module tree but is still active! (ArgumentError)

Our fix was to use .deliver_now and not .deliver_later (this is not a general fix, but it was okey for us). Below there are some debug hints which helped us to locate the problem:

  • We placed a pry debugger in [ActiveSupport#clear](…

Building web applications: Beyond the happy path

When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.

Different screen sizes and browsers

Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?

  • Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
  • Use @media queries to build a responsive design
    • If you do not suppo…

Fixing "identify: not authorized"

Ubuntu has decided to disable PDF processing because ImageMagick and the underlying Ghostscript had several security issues.

When your Ghostscript is up to date (and receiving updates regularly), you can safely reactivate PDF processing on your computer like this:

  1. Open /etc/ImageMagick-6/policy.xml
    • For older versions of Ubuntu (or possibly ImageMagick, the Path is /etc/ImageMagick/policy.xml
  2. Remove/Comment lines after <!-- disable ghostscript format types -->

If you need it enabled for an…

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Drawing diagrams with is a web application that lets you draw flow charts and other diagrams. It works much nicer than office suite tools like LibreOffice Draw.

Its UI is easy to use: Simply drag and drop shapes or arrows from the left-hand side onto your sheet. Drag start/end of arrows to shapes to automatically connect them. You can add text to shapes by selecting them and typing. To add colors, select a shape and use the right-hand panel.

While you can, you don't need to store your charts online. "Offline" storage can be files…

An incomplete guide to migrate a Rails application from paperclip to carrierwave

In this example we assume that not only the storage gem changes but also the file structure on disc.

A general approach

Part A: Create a commit which includes a script that allows you to copy the existing file to the new file structure.

Part B: Create a commit which removes all paperclip logic and replace it with the same code you used in the first commit

Part A

Here are some implementation details you might want to reuse:

  • Use the existing models to read the files from
  • Use your own carrierwave models to write t…

Debugging cucumber feature with javascript + firefox vnc

TL;DR Debugging problems with javascript errors in cucumber tests is sometimes easier in the browser. Run the test, stop at the problematic point (with Then pause from Spreewald 1.7+) and open VNC for Firefox.



Ruby constant lookup: The good, the bad and the ugly

In Ruby, classes and modules are called constants. This card explains how Ruby resolves the meaning of a constant.

The good

E. g. in the following example, Array could mean either Foo::Array or simply Array:

class Foo
  def list

What Ruby does here is to see if the name Array makes sense inside of Foo::, and if that fails, resolves it to ::Array (without a namespace).

The bad

You might be surprised that these are all valid ways to reference Ruby's String class:

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Printing background color of elements

Browsers' printing methods usually don't print background colors. In most cases this is the desired behavior, because you don't want to spent tons of ink printing the background of a web page. But in some cases you want to print the background color of elements, e.g. bars of a chart. For those elements you need to set the following css styles:

Chrome and Safari:

-webkit-print-color-adjust: exact;


color-adjust: exact;

Understanding IRB warning "can't alias ... from ..."

Sometimes, the IRB prints a warning during boot:

irb: warn: can't alias source from irb_source.


During boot, the IRB creates many aliases to give the user quick access to irb functions like source-ing a file.

However, if IRB's context already responds to the alias it wants to create, it will no…

Upgrading a Rails app to Cucumber 3

Upgrade gems

You need to update a lof gems. Make sure you don't have any version constraints in your Gemfile or your bundle update won't do anything!

Upgrade cucumber_priority:

bundle update cucumber_priority

Upgrade spreewald:

bundle update spreewald

Upgrade cucumber_factory:

bundle update cucumber_factory

Upgrade parallel_tests:

bundle update parallel_tests

Even on the latest version, parallel_tests will print some deprecation warnings due to using an older formatter A…

Chrome: Making high-resolution website screenshots without add-ons

If you want to make a screenshot of a website that works well in print or on a high-DPI screen (like Apple Retina displays), here is how you can capture a high-resolution screenshot.

You can do this without an addon:

  • Open the website
  • If you have multiple monitoros:
    • Resize the Chrome window so it covers multiple monitors (in Linux you can hold ALT and resize by dragging with the right mouse button)
    • Zoom into the page using CTRL + and CTRL - so it covers most of the window area. Leave generous padding on the left and right so…

Form letters with LibreOffice Writer

This is painful. Consider using Microsoft Office or switching careers. If you need to write < 20 letters consider doing it manually.

So you didn't listen and here it comes:

  1. Ignore the Mail Merge Wizard. It will crash or destroy your document.
  2. Export your addresses, recipient names, etc. as a .ods spreadsheet (.xls, .xlsx, .ods). Use any columns that work for you, but be consistent. I like to use one column for the address, one column for the salutation line.
  3. Import the spreadsheet as an address book source: *Tools => Add…

How to fix HTML elements being cut off when printing

When you print (or print preview) and elements are cut off (e.g. after 1st page, or "randomly") you should check your CSS rules for these:

  • Is there an element with "display: inline-block" that surrounds your content? Make sure it has "display: block" for printing.
    This primarily affects Firefox and Internet Explorer. Chrome seems to be able to handle inline-block elements in most cases.

  • Does the element itself, or a container, define "overflow: hidden"? Use "overflow: auto" (or maybe "overflow: visible") instead.

  • Is th…

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Cucumber: Identifying slow steps that drag down your test speed

In most projects I know, Cucumber test suite speed is not an issue. Of course, running 350 features takes its time, but still each test for itself is reasonably fast. There is nothing you can do to fundamentally speed up such a test (of course, you should be using parallel_tests).

However, in projects that go beyond clicking around in a web GUI and checking results, there might be various measures to speed things up. Katapult tests for example could be sped up more than 4 times by re…

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