3620 cards

Bundler: How to install version 1 instead of 2 (latest version)

When installing a gem you can use version comparators like >= or ~>. That way it is possible to fetch the latest version of Bundler 1 with this command:

gem install bundler -v '~>1'

How to install bundler for Ruby < 2.3 is a common usecase where you might need Bundler 1.


Git: Show commits that have touched specific text in a file

If you want to find the commits that touched a specific text in a file, use git log -S 'text in the code' -- path/to/file.

Here is an example, where the move of the convert_number_column_value(value) method in active record is traced (simplified output):

git log -n 1 --pretty=oneline -S 'convert_number_column_value(value)' -- activerecord/lib/active_record/base.rb
ceb33f84933639d3b61aac62e5e71fd087ab65ed Split out most of the AR::Base code into separate modules :cake:

git show ceb33f84933639d3b61aac62e5e71fd087ab65ed…


Finding a method name on a Ruby object

Wondering how a specific method on an object is exactly named? You can use Enumerable#grep to detect it in the array of methods.

@user.methods.grep /name/ # => [:name, :first_name, :last_name]

You can also call #private_methods or #public_methods. To find only relevant methods, it is suggested to subtract generic methods like this:

User.methods - Object.methods
User.methods - ActiveRecord::Base.methods
@user.methods - Object.instance_methods
@user.methods - ActiveRecord::Base.instance_methods

Using regular expressions in JavaScript

Regular expressions in Javascript are represented by a RegExp object. There also is a regex literal as in many other languages: /regex/. However, they are used slightly differently.

Regex literal

  • Usage: /foo+/
  • Shorthand for creating a regular expression object

RegExp() object

  • Usage: Regexp("foo+") or new RegExp("foo+")
  • No surrounding slashes required (they're the literal markers)
  • Since the argument is a string, backslashes need to be escaped as well: RegExp("\\d+")


  • Regex objects [never eq…

Heads up: Capybara 3's text matchers no longer squish whitespace by default

Until Capybara 2, node finders that accept a text option were able to find nodes based on rendered text, even if it spans over multiple elements in the HTML. Imagine a page that includes this HTML:

<div class='haystack'>
  Try to match me.

Even though the text is separated by a <br> tag in the HTML, it is matched until Capybara 2 which used to "squish" text prior to the comparison.

# Capyabara 1 or 2


no passenger served applications running error when deploying via capistrano

When deploying with capistrano it's possible you get this "error" message:

*** [err :: example.com] There are no Phusion Passenger-served applications running whose paths begin with '/var/www/example.com'.
*** [err :: example.com] 

This is just because there were no running passenger process for this application on the server which could be restarted. It's not a real error. The application process will start if the first request for this app hits the appserver.

The output appears as err because it's printed to stderr.


How to recognize CVE-2019-5418

If you get requests with values for formats like this:

{:locale=>[:de], :formats=>["../../../../../../../../../../etc/services{{"], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :coffee, :haml]}

or fails like this:

Invalid query parameters: invalid %-encoding (../../../../../../../../../etc/passwd%%0000.html)

Someone tries to exploit CVE-2019-5418.
If you use the latest Rails (or latest Rails LTS) you're…


z-index: About stacking contexts

The CSS property z-index is not as global as you might believe. Actually, it is scoped to a so-called "stacking context". z-indexes only have meaning within their stacking context, while stacking contexts are treated as a single unit in their parent stacking context. This means indices like 99999 should never actually be needed.

Creating a new stacking context

In order to create a stacking context with the least possible side effects, use these properties on an element:

position: relative // or absolute
z-index: 0 // o…


Stop animations and network polling when the document tab isn't visible

Is your application doing something expensive every few seconds? Maybe an animated slider that rotates images? Maybe you are updating data over the network every five minutes?

It's a good idea to pause this if the your document tab is not even visible to the user. This saves your user's battery and data plan.

You can ask document.visibilityState whether this tab is visible:

function pulse() {
if (!document.visibilityState || document.visibilityState =…

Linked contentDeprecated

Execution of shell code in Ruby scripts

Deprecated ways to execute shell code in Ruby

This is just a reference for legacy code. For new code, always use capture3.

%x{ } or backticks – quick and easy

Returns the standard output of running the given command in a subshell. This is an alias for `…`, and you can use string interpolation.


name = 'ls'
result = `which #{name}`

It does not escape anything you inject in the string.

If you want to find out if the call was …

Linked contentDeprecated

How to install npm packages globally without sudo on Linux

All quoted.

  1. Set up a package root in your homedir to hold the Node "global" packages:

    $ NPM_PACKAGES="$HOME/.npm-packages"
    $ mkdir -p "$NPM_PACKAGES"
  2. Set NPM to use this directory for its global package installs:

    $ echo "prefix = $NPM_PACKAGES" >> ~/.npmrc
  3. Configure your PATH and MANPATH to see commands in your $NPM_PACKAGES prefix by adding the following to your .bashrc:

    # NPM packages in homedir

    Tell our environment about user-ins…

Rails Asset Pipeline: Building an Icon Font from SVG Files

Webpacker can automatically create an icon font from SVG files, which is really handy. When you're using the asset pipeline, you can still have an icon font from SVG files, but it requires some manual work.

Creating the icon font

  • Install the NPM package icon-font-generator. If you're not using nvm, run sudo npm install -g icon-font-generator
  • Put all SVG icons for the font into their own directory.
    • The icon name will be taken from the SVG file name
  • Download the attached script and update the Configure

Some hints on upgrading to Unpoly 0.60.0

Unpoly 0.60.0 removed the jQuery dependency to improve performance (see Hennings talk about Javascript without jQuery). I upgraded one of our applications which used a lot of JavaScript with Unpoly compilers and jQuery and want to mention some aspects I had trouble with:

Use up.$compiler as a first step

up.compiler now yields a native DOM element instead of jQuery element. In order to get the old behavior, use up.$compiler. This is u…


Events triggered by jQuery cannot be observed by native event listeners

jQuery has a function $.fn.trigger(). You can use it to dispatch an event on a jQuery object:

let $element = $('.foo')

A caveat is that such an event will be received by jQuery event listeners, but not by native event listeners:

let $element = $('.foo')

$element.on('change', event => console.log('I will be called'))
$element[0].addEventListener('change', event => console.log('I WON'T be called'))


This is currently a WONTFIX for jQuery (see c…

Linked contentAuto-destruct in 6 days

Updated: Fixing flaky integration tests

The section "Tool 5: Ensure no other scenarios are bleeding in" was added.

How to: Migrate from CoffeeScript to ES6

It is quite easy to migrate from CoffeeScript to ES6. You can use decaffeinate to convert your CoffeeScript source to modern JavaScript.


  • Install the NPM module globally yarn global add decaffeinate
  • Add the following line to your ~/.bashrc to export the Yarn binaries in your Bash
export PATH="$PATH:$(yarn global bin)"
  • Run decaffeinate some.coffee to get the converted modern JavaScript file.


  • decaffeinate will add some [suggestions](https://gith…

Why two Ruby Time objects are not equal, although they appear to be

So you are comparing two Time objects in an RSpec example, and they are not equal, although they look equal:

expected: Tue May 01 21:59:59 UTC 2007,
     got: Tue May 01 21:59:59 UTC 2007 (using ==)

The reason for this is that Time actually tracks fractions of a second, although #to_s doesn't say so and even though you probably only care about seconds. This means that two consecutive calls of Time.now probably return two inequal values.

Consider freezing time in your tests so it is not dependent on the speed of the executi…

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