A check if two date or time ranges A and B overlap needs to cover a lot of cases:

1. A partially overlaps B
2. A surrounds B
3. B surrounds A
4. A occurs entirely after B
5. B occurs entirely after A

This means you actually have to check that:

• neither does A occur entirely after B (meaning A.start > B.end)
• nor does B occur entirely after A (meaning B.start > A.end)

Flipping this, A and B overlap iff A.start <= B.end && B.start <= A.end

The code below shows how to implement this in Ruby on Rails. The example is a class `Interv...

This checklist should help you to check edge cases that are not part of the default Carrierwave configuration.

• Check Default Configuration and Suggested Changes
• Use secret URLs.
• Check if you need expiring public URLs.
• Check if you need an optimized cache
• Use a [nested directory structure](https://makandracards.com/m...

Starting with Rails 7.1 the production logger is set to standard out. For applications running with opscomplete ensure to keep logging to a file as before (e.g. when running bin/rails app:update).

It should be enough to change these lines in the config/environments/production.rb back to the implementation in Rails <7.1:

-  # Log to STDOUT by default
-  config.logger = ActiveSupport::Logger.new(STDOUT)
-    .tap  { |lo...

Rails supports time zones, but there are several pitfalls. Most importantly because Time.now and Time.current are completely different things and code from gems might use one or the other.

Especially configuring an application that cares only about one time zone is a bit tricky.

The following was tested on Rails 5.1 but should apply to Rails 4.2 as well.

Using only local time

Your life will be easier if your application does not need to support time zones. Disable them like this:

config.time_zone = 'Berlin' # Your local ...

Also see the list of IRB commands.

Switching the context

Changes the "default receiver" of expressions. Can be used to simulate a "debugger situation" where you are "inside" an object. This is especially handy when needing to call private methods – just invoke them, no need to use send.

• Switch to an object: chws $object
• Reset to main: chws
• Show current context: cwws (usually shown in IRB prompt)

[Technical details](https://technology.doximity.com/articles/the-hidden-gems-of-r...

tl;dr

Prefer request specs over end-to-end tests (Capybara) to joyfully test file downloads!

Why?

Testing file downloads via Capybara is not easy and results in slow and fragile tests. We tried different approaches and the best one is just okay.

Tests for file downloads via Capybara ...

• ... are slow,
• ... are fragile (breaks CI, breaks if Selenium driver changes, ...),
• ... need workarounds for your specia...

Instantiating ActiveRecord objects comes expensive. To speed up things, you can choose a more direct way to talk to your database: the ActiveRecord::ConnectionAdapters::DatabaseStatements module.

Using the module and its methods is not suggested in the usual in-app workflow, as validations, callbacks, custom getters/setters etc. are ignored. However, for database-centered stuff like migrations, these fill the gap between writing pure SQL and full...

Sometimes you need to remove high Unicode characters from a string, so all characters have a code point between 0 and 127. The remaining 7-bit-encoded characters ("Low-ASCII") can be transported in most strings where escaping is impossible or would be visually jarrring.

Note that transliteration this will change the string. If you need to preserve the exact string content, you need to use escaping.

Using ActiveSupport

ActiveSupport comes with a `#tran...

Rails has generic error messages you can define in your locale .yml files. You may override those application-wide error messages using model or attribute scope like this:

en:
  activerecord:
    errors:
      messages:
        invalid: is invalid # used for any invalid attribute in the application
        presence: etc
      models:
        car:
          invalid: does not work # used for invalid car attributes
          attributes:
            driver:
              invalid: not allowed to drive # used if the car's driver attribut...

Rails 7.1 added a new method Rails.env.local?. If you want to stub the Rails env correctly, use ActiveSupport::EnvironmentInquirer like this:

# check if the value of stubbed_env is valid
allow(Rails).to receive(:env).and_return(ActiveSupport::EnvironmentInquirer.new(stubbed_env.to_s))

This are the steps I needed to do to add esbuild to an application that used the vanilla rails asset pipeline with sprockets before.

Preparations

1. update Sprockets to version 4
2. add a .nvmrc with your preferred node version (and install it)
3. add gems jsbundling-rails and foreman to your Gemfile:

   gem 'jsbundling-rails'
   group :development, :test do
     gem 'foreman'
     # ...
   end
   

4. bundle install
5. run bin/rails javascript:install:esbuild in a console to prepare esbuild.
6. run `yarn instal...

Normally, Rails handles encryption and signing of cookies, and you don't have to deal with the matter. Should you need to decrypt a session cookie manually: here is how.

Obviously, you can only decrypt a session cookie from within the corresponding Rails application. Only the Rails application that encrypted a cookie has the secrets to decrypt it.

Rails 7

• With authenticated encryption enabled (default since Rails 5)
• W...

So you added a new callback to your model that (e.g.) caches some data when it is saved. Now you need to run that callback for the 10000 existing records in the production database. You have two options here:

1. Write a clever migration, possibly by embedding the model into the migration script.
2. Open the Rails console after deployment and re-save every single record. You should probably add two chores to your issue tracker so you won't forget t...

I was recently asked to optimize the response time of a notoriously slow JSON API endpoint that was backed by a Rails application.
While every existing app will have different performance bottlenecks and optimizing them is a rabbit hole of arbitrary depth, I'd like to demonstrate a few techniques which could help reaching actual improvements.

The baseline

The data flow examined in this card are based on an example barebone rails app, which can be used to reproduce the r...

It is very common to parse dates from strings. It seems obvious to use Date.parse for this job. However this method does not validate the input and tries to guess the format of the string.

This can lead to a very unexpected results:

Date.parse('Foobar_09_2018')
# Tue, 09 Oct 2018

In most of the cases it would be better to use Date.strptime as you can provide a date or time pattern to match against.

Date.strptime('Foobar_09_2018', '%d_%m_%Y')
# ArgumentError (invalid strptime format - `%d_%m_%Y')

Date.strptime('01_09...

For my computer science bachelor's thesis I programmed and evaluated a CLI Test Case Prioritization (TCP) tool for makandra. It has been written as a Ruby Gem and was tested and evaluated against one Ruby on Rails project. This card will summarize and present the research results, the evaluation and the programmed CLI tool.

The code has been published for educational purposes on GitHub. The german bachelor's thesis has also been included for download at the end.

...

Rails offers a way to prepend (or append) view paths for the current request. This way, you can make the application use different view templates for just that request.

Example

A use case of this is a different set of view templates that should be used under certain circumstances:

class UsersController < ApplicationController

  before_action :prepare_views
  
  def index
    # ...
  end    
  
  private
  
  def prepare_views
    if <condition>
      prepend_view_path Rails.root.join('app', 'views', 'special')
    end
  end
 ...

Rails is split into a large number of (sub-) frameworks.

The most important and central of those are

• activesupport (extends the Ruby standard library)
• activerecord / activemodel (ORM for Rails)
• actionview / actionpack (controller / views)
• actionmailer (sends mails)

However, there are also some more situational frameworks included, such as

• actioncable (real time communications using websockets)
• actionmailbox (receives mails)
• actiontext (support for WYSIWYG text editor)
• activejob (background jobs)
• activestorage (file uplo...

All columns of a model's database table are automagically available through accessors on the Active Record object.

When you need to specialize this behavior, you may override the default accessors (using the same name as the attribute) and simply call the original implementation with a modified value. Example:

class Poet < ApplicationRecord

  def name=(value)
    super(value.strip)
  end

end

Note that you can also avoid the original setter and directly read/write from/to the instance's attribute storage. However this is dis...

Rails offers the fresh_when method to automatically compute an ETag from the given record, array of records or scope of records:

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    fresh_when @user
  end  
  
  
  def index
    @users = User.all.to_a
    fresh_when @users
  end
end

When your view also displays other records (typically associations), those other records should be included in the ETag. You can do so by passing an array of ETaggable objects to fresh_when.

...

When upgrading Rails versions -- especially major versions -- you will run into a lot of unique issues, depending on the exact version, and depending on your app.

However, it is still possible to give some generic advice on how you want to tackle the update in principle.

If you are not really confident about upgrading Rails, have a look at Rails LTS.

How many update steps?

Besides the Rails upgrade itself, you might also want to upgrade your other gems and upgrade your Ruby version.
First decide in how many st...

If you're suffering from a huge de.yml or similiar file, cry no more. Rails lets you freely organize your dictionary files in config/locales.

My organization works like this:

• config/locales/rails.de.yml modified Rails boilerplate
• config/locales/faker.de.yml modified Faker boilerplate
• config/locales/models.de.yml model names, attribute names, assignable_value labels
• `config/locales/views.de.y...

If you are using the routing-filter gem in your Rails 7.1 app for managing URL segments for locales or suffixes, you will notice that the filters do no longer apply, routes are broken and the necessary parameters are no longer extracted. That is because routing-filter patches Rails' find_routes-method to get the current path and apply its defined filters on it. These filters then modify the params that are handed over to your controller action. This way you receive a locale parameter from a ...

Here are some hints on best practices to maintain your tasks in larger projects.

Rake Tasks vs. Scripts

• The Rails default is using rake tasks for your application tasks. These live in lib/tasks/*.
• In case you want to avoid rake for your tasks and just use plain ruby scripts, consider lib/scripts/* as folder.

Keeping tasks slim

For readability and testing it's easier to keep your tasks slim. We suggest to use folders inside the tasks or scripts folder.

Example for a task:

The slim task lib/tasks/gitlab.rb: