Ruby has two different ways to match the start and the end of a text:

• ^ (Start of line) and $ (End of line)
• \A (Start of string) and \z (End of string)

Most often you want to use \A and \z.

Here is a short example in which we want to validate the content type of a file attachment. Normally we would not expect content_type_1 to be a valid content type with the used regular expression image\/(jpeg|png). But as ^ and $ will match lines, it matches both content_type_1 and content_type_2. Using \A and \z will wo...

This note shows how to merge an ugly feature branch with multiple dirty WIP commits back into the master as one pretty commit.

Squashing commits with git rebase

What we are describing here will destroy commit history and can go wrong. For this reason, do the squashing on a separate branch:

git checkout -b squashed_feature

This way, if you screw up, you can go back to your original branch, make another branch for squashing and try again.

Tip

If you didn't make a backup branch and something ...

Somewhat regularly, you will need to filter a list down to some items and then map them to another value.

You can of course chain map and compact, or select/filter and map, but Ruby 2.7 introduced a method for this exact purpose: filter_map.

So instead of

>> [1, 2, 3, 4, 5, 6].map { |i| i * 2 if i.even? }.compact
=> [4, 8, 12]

or

>> [1, 2, 3, 4, 5, 6].select(&:even?).map { |i| i * 2 }
=> [4, 8, 12]

you can just do

>> [1,...

I recently wanted to add a model for address information but also wanted to add a unique index to those fields that is case-insensitive.
The model looked like this:

create_table :shop_locations do |t|
  t.string :street
  t.string :house_number
  t.string :zip_code
  t.string :city
  t.belongs_to :shop
end

But how to solve the uniqueness problem?

Another day, another undocumented Rails feature!

This time, it’s that ActiveRecord::Base.connection.add_index supports an undocumented option to pass a string argument as the v...

Imagine these models and associations:

class Deck < ApplicationRecord
  has_many :cards
end

class Card < ApplicationRecord
  belongs_to :deck, optional: true
end

Now you want to find all Decks without any Card or all Cards without a Deck.

Rails 6.1+

Rails 6.1 introduced a handy method ActiveRecord#missing to find records without given associations.

Deck.where.missing(:cards)

SELECT "decks".*
FROM "dec...

When changing code in mailers, updating the corresponding mailer preview can be forgotten very easily.

Mailer previews can be tested like other code as well and I sometimes add the following tests to test suites:

# Make sure to require the previews
Dir[Rails.root.join('spec/mailers/previews/*.rb')].each { |file| require(file) }


ActionMailer::Preview.all.index_with(&:emails).each do |preview, mails|
mails.each do |mail|
    describe preview do
      specify "##{mail} works" do
        expect { preview.call(mail...

When redirecting you should take care to use the right HTTP status code.

From controllers

When redirecting from a controller, the default status code is 302 Found (aka Moved Temporarily):

red...

If you have a JS fiddle, you can open it in fullscreen by appending /show to the URL.

Example: https://jsfiddle.net/b275g910/3 => https://jsfiddle.net/b275g910/3/show

When starting a project we always make a good estimate of all known requirements, and plan budgets and available developers accordingly.

Requirements change. Budgets usually don't.

To make sure a project stays on track, we update our estimates once a month and compare them to the remaining budget. If this doesn't match any more, we have to act.

To update an estimate, do the following:

• Start with the most recent estimate for the project.
• Which stories have been completed? Set their estimate to zero.
• Have any requirements cha...

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

Checklist

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...

Recent IRB versions include a multi-line autocomplete which may be helpful to novice users but can be distracting.

Cycling through options works by pressing the Tab key (as usual), and for some methods you also get some kind of documentation, though the quality of results is usually not on par with your IDE of choice.

I have found that it also slows down my IRB in some cases, or that pressing the Backspace key does not always reliably remove characters, which I find more annoying than useful.

You may disable multi-line autocomplete by

• ...

We're always striving towards keeping our website's JavaScript as small as possible.

If you're using webpack(er), you can use the webpack-bundle-analyzer plugin to get a good overview, which of your JavaScript modules take up how much space, and where you can optimize.

To use it, add it via npm or yarn

yarn add webpack-bundle-analyzer

Then add this to your environment.js:

// Uncomment this code to show statistics of bundle sizes. Generated file will automatically...

There was an issue with makandra_sidekiq < 0.2 concerning the stopping of Sidekiq.

Sidekiq < 6 has two finishing timeouts: one for finishing things itself (A), and one for sidekiqctl before killing a running Sidekiq instance (B). While USAGE banner of sidekiqctl advises to have B always greater than A, makandra_sidekiq < 0.2 runs sidekiqctl without passing a timeout. If the Sidekiq instance is configured with a timeout higher than the default 10s timeout of sidekiqctl, `sideki...

Testing file download links in an end-to-end test can be painful, especially with Selenium.

The attached download_helpers.rb provides a download_link method for your Capybara tests. It returns a hash describing the download's response:

details = download_link('Download report')
details[:disposition]  # => 'attachment' or 'inline'
details[:filename]     # => 'report.txt'
details[:text]         # => file content as string
details[:content_type] # => 'text/plain'

Features

Compared to [other approaches](...

Ruby's __FILE__ keyword returns the path to the current file. On popular for this are Ruby binaries:

#!/usr/bin/env ruby
$LOAD_PATH << File.expand_path('../../lib', __FILE__)
require 'my_cli'
MyCli.run!

However, if you create a symlink to this file, this will no longer work. __FILE__ will resolve to the path of the symlink, not to its target.

One solution is to use File.realpath(__FILE__).

In Ruby 2+ you can also use this:

$LOAD_PATH << File.expand_path('../lib', __dir__)

__dir__ is simply a shortcut for `...

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...

Current webkit browsers like Chrome and Safari have a special variable in their consoles that refers to the selected DOM node in the elements panel. This lets us easily inspect Angular scopes.

0. Right click in the page and click "Inspect" to open the Dev Tools

1. Select the element you're interested in from the elements panel

2. Focus the console (in Chrome, hit ESC)

3. Get the scope object and store it

   s=$($0).scope()
   
   // That is:
   element = $0 // Store element
   $element = $(element) // Wrap with j...
   

While verifying doubles in RSpec is a good default, it is limited in the amount of methods it actually is able to verify.

The background is that RSpec can't verify dynamically defined methods, which is a known issue for the usage of helper_method and also the reason why [RSpec >= 3.6](http://rspec.info/blog/2017/05/rspec-3-6-has-been-rel...

Tempfiles get deleted automatically

With the the ruby Tempfile class you can create temporary files. Those files only stick around as long as you have a reference to those. If no more variable points to them, the GC may finalize the object at some point and the file will be removed from the filesystem. If you would try to access your tempfile then using its path (which you stored previously), you would get an error because the file no longer exists.

Unlink your tempfiles when you're done with them
-...

Chrome gives you the currently selected element in the inspector with $0. If you select a button in the DOM you can set and inspect the event handler with the following two code lines:

$($0).on('click', function() { console.log('Hello') })

jQuery._data($0, "events").click[0].handler
// => "function () { console.log('Hello') }"

This is useful for debugging.

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...