We had a card that described how to install multiple mysql versions using mysql-sandbox. Nowadays with the wide adoption of docker it might be easier to use a MySQL docker image for this purpose.

Create a new mysql instance

docker run --name projectname_db -e MYSQL_ROOT_PASSWORD=secret -p "33008:3306" -d --restart unless-stopped mysql:5.7

The port 33008 is a freely chosen free port on the host machine that will be used to establish a con...

Looks simpler than inaction_mailer:

gem install mailcatcher
mailcatcher

Setup Rails to send mails to 127.0.0.1:1025. Usually you want the following config in config/environments/development.rb and maybe in test.rb or cucumber.rb.

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  :address => 'localhost',
  :port => 1025
}

Now you can see sent mails in your browser when opening http://127.0.0.1:1080

Note: In order to s...

In Selenium features the server and client are running in separate processes. Therefore, when mocking time with a tool like Timecop, the browser controlled by Selenium will still see the unmocked system time.

timemachine.js allows you to mock the client's time by monkey-patching into Javascript core classes. We use timemachine.js in combination with the Timecop gem to synchronize the local browser time to the ...

When accepting GIF images, you will also accept animated GIFs. Resizing them can be a time-consuming task and will block a Rails worker until the image is processed.

Save yourself that trouble, and simply tell ImageMagick to drop any frames but the first one.

Add the following to your uploader class:

process :remove_animation

private

def remove_animation
  if content_type == 'image/gif'
    manipulate! { |image| image.collapse! }
  end
end

You may also define that process for specific versions only (e.g. only for thum...

Given there is a user with an attachable avatar:

class User < ApplicationRecord
  has_one_attached :avatar
end

If you want to add a preprocessed version follow these steps:

1. Add the named version and deploy

class User < ApplicationRecord
  has_one_attached :avatar do |attachable|
    attachable.variant :preview, resize_to_fit: [177, 177 * 9 / 16], preprocessed: true
  end
end

2. Preprocess this version for all existing records `bundle exec rails runner 'User.find_each { |user| user.avatar.variant(:preview).proc...

This card explains how to install RubyMine for the first time. If you want to upgrade an existing RubyMine installation (after legacy install) to a newer version, see How to upgrade RubyMine.

Option A (new way)

Ubuntu 16.04 comes with snap, a way to package software with all its dependencies. RubyMine is also packaged as a snap.

A snap will always track a channel (like stable, beta) and automatically update to the newest version available in this channel. By default the snap daemon will check for ...

Your after_commit callbacks will not know about changes, as Rails discards them when committing.

The linked article shows a clever trick to work around that: It uses an after_save method that looks at changes and writes its decision to an instance variable. That instance variable can then be used in the after_commit method.

Note that while callbacks like after_save are not affected, there are valid reasons for using only after_commit, and not after_save. Enqueueing a Sidekiq job is just one of them.

Rails 5+

You can use ...

Debugging your integration tests, that run a headless Chrome inside a docker image, is tricky.

In many cases you can connect your Chrome to a remote docker container like docker-selenium, which should be the preferred way when you try to inspect a page within your integration test.

Otherwise you might be able to start your docker container with --net=host and access your local chromedriver in the host address space host.docker.internal.

If both options above don't work for you here is a...

Ruby has this handy block shortcut map(&:to_i) for map { |x| x.to_i }. However, it is limited to argument-less method invocations.

To call a method with an argument, you usually need to use the full block form. A common and annoying case is retrieving values from a list of hashes (imagine using a JSON API):

users = [ { name: 'Dominik', color: 'blue' }, { name: 'Stefan', color: 'red'} ]
names = users.collect do |user|
  user[:name]
end

If you're using Rails 5+, this example is covered by Enumerable#pluck (`users.pluck(:name)...

Rails 6.1 has a "strict loading" mode that forces the developer to preload any association they plan to use. Associations no longer load lazily. An error is raised when reading an association that was not preloaded.

Enabling strict loading is a tool to prevent n+1 queries.

Strict loading can be enabled for individual records, for a single association,...

As an application exists, data accumulates. While you'll be loosely monitoring the main models' record count, some supportive database tables may grow unnoticed.

To get a quick overview of database table sizes, you can view the row count like this:

PostgreSQL

SELECT schemaname,relname,n_live_tup 
FROM pg_stat_user_tables 
ORDER BY n_live_tup DESC
LIMIT 12;

 schemaname |                    relname                     | n_live_tup 
------------+------------------------------------------------+------------
 public     | images...

How it works

See the lemonade descriptions.

Unfortunately, the gem has a few problems:

• it does not work with Sass2
• it always generates all sprites when the sass file changes, which is too slow for big projects
• it expects a folder structure quite different to our usual

All these problems are solved for us, in our own lemonade fork. This fork has since been merged to the original gem, maybe we can use t...

In a nutshell:

If you require your Rails models manually, pay attention to the path you use. Unless you have to, don't do it at all.

Background

Consider these classes:

# app/models/user.rb

class User < ActiveRecord::Base
  validate :magic

  def magic
    errors.add_to_base('failed') if bad_things?
  end
end

^
# app/models/foo.rb

require 'user'

class Foo
  # something happens here
end

Now, when your environment is booted, Rails will automatically load your models, like User...

tl;dr: Do not use merge! for session hashes. Use update instead.

Outline

Let's assume you're modifying the Rails session. For simplicity, let's also assume your session is empty when you start (same effect when there is data):

# In our example, we're in a Rack middleware
request = Rack::Request.new(env)
request.session.merge! :hello => 'Universe'
request.session
=> {}

Wat?

Even worse: When you inspect your request.session like above (e.g. in a debugger shell, o...

You've been there: A form cannot be submitted, but you don't see a validation error because the field at fault has no corresponding input field on the form. Because this is usually a bug, you insert debug information listing all errors into the form view. And once the bug is fixed, you forget to take out that debug information.

There is a better way. By copying one of the attached initializers into config/initializers, your forms will always render a small box listing all form errors in the bottom right corner of the screen. This box is n...

If you're on Ruby 2.3+ there's a <<~ operator to automatically unindent HEREDOCs:

str = <<~MESSAGE
  Hello Universe!
  This is me.
             Bye!
MESSAGE

If you have an older Ruby, you can use the String#strip_heredoc method from ActiveSupport. See Summarizing heredoc in ruby and rails for an example.

Technically...

Rails comes with grouped_collection_select that appears to be useful, but isn't.

As an alternative, consider the flat_grouped_collection_select found below. It takes a third argument that extracts the group from each element in the collection:

= form.flat_grouped_collection_select :user_id, users, :department, :id, :full_name

Here is the monkey-patch:

class ActionView::Helpers::FormBuilder

  def flat_grouped_collection_selec...

SimpleForm is a great approach to simplifying your forms, and it comes with lots of well-defined input types. However, the :grouped_select type seems to be overly complicated for most use cases.

Example

Consider this example, from the documentation:

form.input :country_id, collection: @continents,
  as: :grouped_select, group_method: :countries

While that looks easy enough at a first glance, look closer. The example passes @continents for a country_id.\
SimpleForm actua...

If you migrate a Rails application from Sprockets to Webpack(er), you can either transpile your CoffeeScript files to JavaScript or integrate a CoffeeScript compiler to your new process. This checklist can be used to achieve the latter.

1. If you need to continue exposing your CoffeeScript classes to the global namespace, define them on window directly:

-class @User
+class window.User

2. Replace Sprocket's require statement with Webpacker's...

TLDR: This card explains which threads and processes interact with each other when you run a Selenium test with Capybara. This will help you understand "impossible" behavior of your tests.

When you run a Rack::Test (non-Javascript) test with Capybara, there is a single process in play. It runs both your test script and the server responding to the user interactions scripted by your test.

A Selenium (Javascript) test has a lot more moving parts:

1. One process runs your test script. This is the process you...

Remember How to skip Sprockets asset compile during Capistrano deployment and Automatically skipping asset compilation when assets have not changed? Turns out there is an even better way to speed up Capistrano deployments with asset compilation – and it's even simpler.

Adding the asset cache directory to symlinked directories

Popular asset managers for Rails are Sprockets and Webpacker. Both keep a cache of already compiled files that we're going to leverage for deployments now.

• Sprockets cache...

When storing files for lots of records in the server's file system, Carrierwave's default store_dir approach may cause issues, because some directories will hold too many entries.

The default storage directory from the Carrierwave templates looks like so:

class ExampleUploader < CarrierWave::Uploader::Base
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
end

If you store files for 500k records, that store_dir's parent directory will have 500k sub-directories which will cause some...

By default, Cucumber uses mocha. This note shows to use RSpec stubs and mocks instead.

Rspec 1 / Rails 2

Put the following into your env.rb:

require 'spec/stubs/cucumber'

Rspec 2 / Rails 3

Put the following into your env.rb:

require 'cucumber/rspec/doubles'

Note: Since Cucumber 4 it is important to require these lines in the env.rb and not any other file in support/* to register the hooks after any other After hook in support/*. Otherwise your doubles are removed, while other After steps requi...

If you want to make your Rails application be capable of sending SMTP emails, check out the action mailer configuration section in the Ruby on Rails guide.

TL;DR you will end up having an smtp_settings hash that looks something like this:

smtp_settings = {
  address: ...,
  domain: ...,
  port: ...,
  user_name: ...,
  password: ...,
  authentication: ...,
  tls: ...,
  enable_starttls_auto: ...,
}

This hash can be set as the `delivery_me...