Capybara will fail to find <a> tags that are missing an href attribute. This will probably happen to you every now and then on JavaScript-heavy applications.

An example would be an AngularJS application where the following HTML actually works. [1]

<a ng-click="hello()">Hello</a>

Capybara will fail to find that link, even though looking it up via the DOM shows it:

>> find_link("Hello")
Capybara::ElementNotFound: Unable to find link "Hello"

>> find("a").text
=> "Hello"

To make find_link and click_link work…

Spammers have started abusing other application to send their spam. This works like this:

• The application has some form that allows to send e-mails to arbitrary users. This can be something like a newsletter sign-up with a double-opt in, a registration confirmation e-mail (or even password reset e-mail), or something similar.
• The e-mail also includes some reflected text. For example, a user may be able to give their name, and the name is used within the e-mail. The spammer will then abuse that text to include his advertisment.

Potentia…

In Rails 3+, you can use:

class Project
  delegate :url_helpers, to: 'Rails.application.routes'

  def project_path
    url_helpers.project_path(self)
  end
end

For Rails 2, use the attached Modularity trait. It will give any Ruby class a method #url_writer, on which you can call URL helpers:

class Foo
  does 'write_urls'
  def self.class_method
    url_writer.session_path
  end
  def instance_method
    url_writer.project_path(5)
  end
end

Why string sorting sucks in vanilla Ruby

Ruby's sort method doesn't work as expected with German umlauts:

["Schwertner", "Schöler"].sort
=> ["Schwertner", "Schöler"] # you probably expected ["Schöler", "Schwertner"]

Also numbers in strings will be sorted character by character which you probably don't want:

["1", "2", "11"].sort
# => ["1", "11", "2"] # you probably expected ["1", "2", "11"]

Also the sorting is case sensitive:

["a", "B"].sort
# => ["B", "a"] # yo...

When building an application that sends e-mails to users, you want to avoid those e-mails from being classified as spam. Most obvious scoring issues will not be relevant to you because you are not a spammer.

However, your application must do one thing by itself: When sending HTML e-mails, you should include a plain-text body or tools like SpamAssassin will apply a significant score penalty. Here is how to do that automatically.

1. Add premailer-rails to your Gemfile and bundle.
2. Done! …

Scrolling overflowing elements with JavaScript

HTML elements with overflow-y: auto or overflow-y: scroll will get a scrollbar when their content is higher than their own height.

When you scroll an element , the element's scrollTop property is updated with the scrollbar's new position. You can also set element.scrollTop = 30 to scroll the element to a vertical pixel position counted from the top.

Scrolling the main viewport with JavaScript

The browser's main document viewport is also scrollable by default. The element that …

This card tries to summarize by example the different uses of heredoc.

• In Ruby << vs. <<- vs. <<~
• In Rails strip_heredoc vs. squish

strip_heredoc should be used for a text, where you want to preserve newlines. (multi-line -> multi-line)

squish should be used for a text, where you want to squish newlines. (multi-line -> one-line)

Ruby 2.3+

def foo
  bar = <<~TEXT
    line1
    line2
    line3
  TEXT
  puts bar.inspect
end
foo => "line1\nline2\nline3\n"

Read more: [Unindent HEREDOCs in Ruby 2.3](/makan…

Suggested Workflow

Set the ruby version in .ruby-version to 2.3.5, then perform these steps one by one, fixing errors as they occur:

1) Update gems as listed below, and bundle
2) Boot a Rails console - see below for a list of changes you will probably need
3) Run Specs with --backtrace option
4) Run Cucumber features (with Geordi's --debug option)
5) When all tests are green, look through your Gemfile and remove as many version constraints as possible.
6) Boot the application in different environements to spot further issues, e…

What collapsing margins are

Imagine you have 2 HTML boxes. The first one has a margin-bottom of let's say 30px and the second one a margin-top of 20px. After rules of collapsing margins have been applied we have a margin of 30px (not 50px) between these two boxes (see this article for an illustration) . This is because no addition of both margins takes place but the maximu…

When using virtual attributes, the attached trait can be useful to automatically copy errors from one attribute to another.

Here is a typical use case where Paperclip creates a virtual attribute :attachment, but there are validations on both :attachment and :attachment_file_name. If the form has a file picker on :attachment, you would like to highlight it with errors from any attribute:

class Note < ActiveRecord::Base
  has_attached_file :attachment
  validates_attachment_presenc...

In ruby you can easily read and write CSVs with the standard CSV library class.

On top of this, you can use the gem smarter_csv for reading (not writing) CSVs in a more comfortable way:

• Keep in mind, that the development of this gem is in an unknown state and the 2.0 release seems to happen never
• The API will change completely for 2.0, so you might find a bunch of unrelated documentation for 1.2

Here is an example…

When you generate a URL in a mailer view, ActionMailer will raise an error unless you previously configured it which hostname to use. Configuring the correct hostname is quite annoying when you have multiple deployment targets with different hostnames, e.g. a staging server and a production server.

Using the hack below you don't need to configure a default hostname for your mailers. They will always use the hostname for the current request:

class ApplicationController < ActionController::Base

  before_filter :make_action_maile...

The Ace editor is a great enhancement when you want users to supply some kind of code (HTML, JavaScript, Ruby, etc).
It offers syntax highlighting and some neat features like auto-indenting.

Integrating it with Webpack as described in the documentation – by using ace-builds and ace-builds/webpack-resolver – failed pretty hard for me. Maybe because Rails' Webpacker is still on Webpack 2.
The following works for Ruby on Rails with Webpacker / Webpack 2.

1. Do not use the `ace-builds…

Rails migrations allow you to use a change method whose calls are automatically inverted for the down path. However, if you need to some path-specific logic (like SQL UPDATE statements) you can not define up and down methods at the same time.

If you were to define define all 3 of them, Rails would only run change and ignore up and down. However, Rails 4+ features a helper method called reversible:

class MyMigration < ActiveRecord::Migration

  def...

Use protocol independent URLs whenever possible so that the browser will choose the protocol related to the protocol which the page is delivered with.

Example issues

• When your page is delivered via https and you provide a youtube video only via http the most browsers (e.g. Firefox, Chrome) won't display the video.
• When you deliver your youtube video via https://youtu.be/jyElDp98HdI your test which checks that the embeded video is rendered in the view will fail because your test server doesn't use https

Solution

Let your lin…