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...

This is a small example on how you can check if your Postgres index can be used by a specific query in you Rails application. For more complex execution plans it might still be a good idea to use the same path of proof.

1. Identify the query your application produces

query = User.order(:last_name, :created_at).to_sql
puts query
# => SELECT "users".* FROM "users" ORDER BY "users"."last_name" ASC, "users"."created_at" ASC

2. Add an index in your migration and migrate

add_index :users, [:last_name, :created_at]...

Rails credentials are a way to store secrets in an encrypted YAML file. Usage is simple: each key in the credentials file becomes a method on Rails.application.credentials, returning the corresponding secret.

# Credentials file
file_storage_secret: superstrongsecret

# Somewhere in the application
FileStorage.secret = Rails.application.credentials.file_storage_secret

Since credentials usually are different between environments, you can easily forget to define them for another environment. If it is an API token, you'll...

Ruby and Rails have several methods for creating a new object that looks like another: clone, dup, deep_dup. When using them you should be aware of their differences so that you can select the method you really need.

clone

• Shallow copy: references to other objects/values are copied (instead of cloning those objects/values)
• Clones the object and all its "special object attributes" like frozen, tainted and modules that the object has been extended with
• [Ruby 2.6 documentation for clone](https://devdocs.io/ruby~2.6/obj...

Localizing a non-trivial application can be a huge undertaking. This card will give you an overview over the many components that are affected.

When you are asked to give an estimate for the effort involved, go through the list below and check which points are covered by your requirements. Work with a developer who has done a full-app localization before and assign an hour estimate to each of these points.

Static text

• Static strings and template text in app must be translated: Screens, mailer templates, PDF templates, helpe...

When Rails releases a new version of their gems, they also release a number of npm packages
like @rails/activestorage or @rails/actioncable.

Unfortunately Rails uses up to 4 digits for their gem version, while npm only allows 3 digits and a pre-release suffix.

To map gem versions and npm versions, Rails is going to use a naming scheme like this:

To reverse lookup a fixture by its table name and id, use the following approach on ActiveRecord::FixtureSet:

table = 'users'       # Specify the fixture table name
id = 123122           # Specify the ID to look for

# Find the fixture that matches the given ID
ActiveRecord::FixtureSet.all_loaded_fixtures[table].fixtures.find { |key, value| value['id'] == id }

Result Example:

[
  "one", # Fixture name
  #<ActiveRecord::Fixture:0x00007e79990234c8>, # ActiveRecord::Fixture object
  @fixture= { ... }, # The raw fixtu...

You can improve your LIKE / ILIKE search queries in PostgreSQL by adding a GIN index with an operate class ("opclass") to split the words into trigrams to the required columns.

Example

class AddSearchTextIndexToUsers < ActiveRecord::Migration[7.1]
  def change
    enable_extension 'pg_trgm'

    add_index :users, :search_tex...

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...

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

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 `#tr...

Git diffs show the surrounding contexts for diff hunks. It does so by applying regular expressions to find the beginning of a context. When it comes to Ruby, however, it will not find method heads and travel up to the class definition:

@@ -24,7 +24,7 @@ class TicketPdf # <=== Actually expected here: the method definition
     ApplicationController.render(
       "tickets/index.html.haml",
       layout: "tickets",
-      assigns: { tickets: tickets }
+      assigns: { tickets: tickets, event_name: event_name }
     )
   end
 end
```...

Most of the time, it's a good default to add a unique index on the foreign key when using Rails’ has_one relationship. This ensures the database enforces the 1:1 constraint and raises an error if your application logic ever violates it.

class User < ApplicationRecord
  has_one :session, dependent: :destroy
end

class Session < ApplicationRecord
  belongs_to :user
end

create_table :users do |t|
  t.timestamps
end

create_table :sessions do |t|
  t.references :user, null: false, foreign_key: true, index: { unique: true ...

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...

When your controller action raises an unhandled exception, Rails will look at the exception's class and choose an appropriate HTTP status code and error page for the response.

For instance, an ActiveRecord::RecordNotFound will cause Rails to render a red "The page you were looking for doesn't exist" with a status code of "404" (not found).

The mapping from exception classes to error types is a hash in Rails.configuration.action_dispatch.rescue_responses. The...

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](/m...

This card describes different flavors for concatting HTML safe strings in a helper method in Rails. You might want to use the tag helper instead of the content_tag helper (the tag helper knows all self closing tags).

Example

We want to generate HTML like this:

<h1>Navigation</h1>
<ul>
  <li>Left</li>
  <li>Right</li>
</ul>

Below you ca...

Leaving old unused DB columns around after a migration is confusing for other developers. However, dropping columns too eagerly might also cause problems and extra work. If you want to mark columns for future deletion, but you are unsure, whether you can simply drop them right now, use these tools:

Add a comment to your DB schema

With schema comments you can add a comment like LEGACY as of yyyy-mm-dd to your DB schema.

Ignore the column

With [...

#pluck is commonly used as a performant way to retain single database values from an ActiveRecord::Relation

Book.pluck(:title, :price) #=> [["The Hobbit", "8.99"], ["The Alchemist", "7.89"]]

But #pluck can do more: you can query multiple tables as well!

Book.joins(:author).pluck("books.title, books.price, authors.name") #=> [["The Hobbit", "8.99", "J. R. R. Tolkien"], ["The Alchemist", "7.89", "Paulo Coelho"]]

Note the use of :author for the joins, and then authors for the pluck clause. The first corresp...

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...

Short reference on how to quickly debug the vanilla Rails job adapters.

Queue Adapters by Environment

Development (:async)

Jobs run in background threads ([Concurrent Ruby ThreadPoolExecutor](https://ruby-concurrency.github.io/concurrent-ruby/maste...

All direct child directories of app are automatically added to the eager- and autoload paths. They do NOT create a module for namespacing. This is intuitive, since there normally is no module Model, or module Controller. If you want to add a new base directory, there's no additional config needed.

Example

app
├── controllers
├── helpers
├── inputs # No config needed 
├── mailers
├── models
├── uploaders # No config needed
├── util # No config needed
└── workers # No config needed

Sometimes it's handy to group files wit...

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...

In Rails 7.2 the new default for config.action_dispatch.show_exceptions is rescuable.

• :rescuable: It will show a Rails error page in the response only for rescuable exceptions as
  defined by ActionDispatch::ExceptionWrapper.rescue_responses. In the
  event of an unexpected internal server error, the exception that caused
  the error will still be raised within the test so as to provide a useful
  stack trace and a good debugging experience.
• :all: It wi...