As your Rails project grows, you will accumulate a number of small patches. These will usually fix a bug in a gem, or add a method to core classes.

Instead of putting many files into config/initializers, I recommend to group them by gem in lib/ext:

lib/
  ext/
    factory_girl/
      mixin.rb
    carrierwave/
      change_storage.rb
      fix_cache_ids.rb
      sanitize_filename_characters.rb
    ruby/
      range/
        covers_range.rb
      array/
        dump_to_excel.rb
        xss_aware_join.rb
      enumerable/
    ...

Background:

ActiveType::Object inherits from ActiveRecod::Base and is designed to behave like an ActiveRecord Object, just without the database persistence.

Don't remove any of the default behavior of the initialize method!

If you have a class which inherits from ActiveType::Object and you need to override the #initialize method, then you should be really careful:

• Always pass exactly one attribute. ActiveRecod::Base objects really want to get their arguments processable as keyword arguments. Don't change the syntax, or y...

The problem

If you're experiencing that your bundle install command fails with an error message like this, rubygems.org might have issues with their ipv6 connectivity:

$ bundle install
Fetching source index from https://rubygems.org/

Retrying fetcher due to error (2/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/ due to underlying error <timed out (https://rubygems.org/specs.4.8.gz)>

The (a little bit dirty) possible solution

If that's actually the case, then you can try to deprioritize the ipv...

The problem

Unpoly's [up-observe], [up-autosubmit] and [up-validate] as well as their programmatic variants up.observe() and up.autosubmit() are a nightmare for integration tests.

Tests are usually much faster than the configured up.form.config.observeDelay. Therefore, it may happen that you already entered something into the next field before unpoly updates that field with a server response, discarding your changes.

The steps I wait for active ajax requests to complete (if configured) and capybara-lockstep can catch some ...

tl;dr

Since Rails 7+ you can use ComparisonValidator for validations like greater_than, less_than, etc. on dates, numerics or strings.

Example

We have a model for booking a trip. This model has mandatory attributes to enforce dates for the start and the end.

# == Schema Information
#
# start_date :date
# end_date   :date
# ...

class TripBooking < ApplicationRecord
  validates :start_date, presence: true
  validates :end_date, presence: true
end

These validations are enough. We also want to ensure, th...

Say you have a User with a Carrierwave attribute #avatar:

class User < ActiveRecord::Base
  mount_uploader :avatar, AvatarUploader
end

When whitelisting the avatar field in the controller, you might do this:

params[:user].permit(:avatar)

But you probably want this:

params[:user].permit(:avatar, :avatar_cache, :remove_avatar)

In this example:

• :avatar_cache allows a newly upload image to persist through form roundtrips in the case of validation errors (something that isn't possibl...

tl;dr

git checkout is the swiss army of git commands. If you prefer a semantically more meaningful command for branch related tasks, use git switch instead.

You can use git switch since git 2.23.

Switch Branch

git branch
# * master
#   feature-branch

git switch feature-branch
git branch
#   master
# * feature-branch

git switch -
git branch
# * master
#   feature-branch

Info

For this use case you can of course also use git checkout.

Switch on a Remote Branch

git branch -a
# * m...

Ncdu is a disk usage analyzer with an ncurses interface. It is designed to find space hogs on a remote server where you don’t have an entire graphical setup available, but it is a useful tool even on regular desktop systems. Ncdu aims to be fast, simple and easy to use, and should be able to run in any minimal POSIX-like environment with ncurses installed.

Alternatives

• du -hs * | sort -h
• Disk Usages Analyser

You can use ETags to allow clients to use cached responses, if your application would send the same contents as before.

Besides what "actually" defines your response's contents, your application probably also considers "global" conditions, like which user is signed in:

class ApplicationController < ActionController::Base

  etag { current_user&.id }
  etag { current_user&.updated_at }

end

Under the hood, Rails generates an ETag header value like W/"f14ce3710a2a3187802cadc7e0c8ea99". In doing so, all objects from that etagge...

Here are a few common patterns that will probably lead to flaky specs. If you notice them in your specs, please make sure that you have not introduced a flaky spec.

Using RSpec matchers

One rule of thumb I try to follow in capybara tests is using capybara matchers and not plain rspec matchers.

One example:

visit(some_page)
text_field = find('.textfield')
expect(text_field['value']).to match /pattern/

This can work, but is too brittle and flaky. match will not retry or synchronize the value of text_field.

The equivale...

Detecting if a Javascript is running under Selenium WebDriver is super-painful. It's much easier to detect the current Rails environment instead.

You might be better of checking against the name of the current Rails environment. To do this, store the environment name in a data-environment of your <html>. E.g., in your application layout:

<html data-environment=<%= Rails.env %>>

Now you can say in a pi...

In MySQL comparing zero to a string 0 = "any string" is always true!

So when you want to compare a string with a value of an integer column, you have to cast your integer value into a string like follows:

SELECT * from posts WHERE CAST(posts.comments_count AS CHAR) = '200' 

Of course this is usually not what you want to use for selecting your data as this might cause some expensive database operations. No indexes can be used and a full table scan will always be triggered.

If possible, cast the compared value in your application to...

New versions of wkhtmltopdf dissallow file:// URLs by default. You can allow them by passing --enable-local-file-access.

If you are using PDFKit, set the option

PDFKit.configure do |config|
  config.default_options = {
    enable_local_file_access: true,
  }
end

This will be necessary in many setups to allow wkhtmltopdf to fetch assets (such as stylesheets) from the filesystem.

Note on security

Allowing this poses some risk when you render user input, since it might be feasible to include data from the local filesyste...

The robots.txt file and <meta name="robots"> HTML tag can be used to control the behavior of search engine crawlers. Both have different effects.

robots.txt

Marking a URL path as "disallowed" in robots.txt tells crawlers to not access that path.

robots.txt is not a guarantee for exclusion from search engine results.

A "disallowed" URL might be known from an external link, and can still be displayed for a matching search.
Example: even if /admin is disallowed in robots.txt, `/admin/som...

If the project team consists of at least 2 members, do a daily standup. It should not take much longer than 15 minutes.

Format

Tell everyone else

• what you did yesterday
• what you intend to do today
• where you might need help or other input
• if there are new developments everyone needs to know about

A "still working on X, will probably be done today" is totally fine. No need to tell a long story.

If you are out of work, find a new story with the others.

If there are new stories in the backlog, look at them and

• make sure ev...

Ruby's standard library includes a class for creating temporary directories. Similar to Tempfile it creates a unique directory name.

Note:

• You need to use a block or take care of the cleanup manually
• You can create a prefix and suffix e.g. Dir.mktmpdir(['foo', 'bar']) => /tmp/foo20220912-14561-3g93n1bar
• You can choose a different base directory than Dir.tmpdir e.g. `Dir.mktmpdir('foo', Rails.root.join('tmp')) => /home/user/rails_example/tmp/foo20220912-14...

If you want to see the git history of a project file, that doesn't exist anymore, the normal git log <path_to_file> won't work. You have to add certain flags to make it work:

git log --all --full-history -- <path_to_file>

tl;dr

Since Rails 6+ you can use before? and after? to check if a date/time is before or after another date/time.

Example

christmas = Date.parse('24.12.2022')
date_of_buying_a_gift = Date.parse('12.12.2022')

date_of_buying_a_gift.before?(christmas)
# => true
# Now you are well prepared for Christmas!! ;)

date_of_buying_a_gift = Date.parse('26.12.2022')

date_of_buying_a_gift.after?(christmas)
# => true
# Now you are too late for christmas! :(

Hint

If you want to check if a date/time is between to ot...

A memory leak is an unintentional, uncontrolled, and unending increase in memory usage. No matter how small, eventually, a leak will cause your process to run out of memory and crash.

If you have learned about a memory leak, looking at the number of Ruby objects by type can help you track it down:

> pp ObjectSpace.count_objects
{:TOTAL=>77855,
 :FREE=>4526,
 :T_OBJECT=>373,
 :T_CLASS=>708,
 :T_MODULE=>44,
 :T_FLOAT=>4,
 :T_STRING=>65685,
 :T_REGEXP=>137,
 :T_ARRAY=>984,
 :T_HASH=>87,
 :T_STRUCT=>12,
 :T_BIGNUM=>2,
 :T_FILE=>3,
 :T_D...

For Rails models where only one of multiple attributes may be filled out at the same time, there is no built-in validation.

I've seen different solutions in the wild, each with different downsides:

• Private method referenced via validate: works, but is barely portable and clutters the model.
• Multiple presence validations with "if other is blank" each: looks pretty, but is incorrect as it allows both values to be filled in; also the error messages for a blank record are misleading.

Here is a third option: Write a custom validator to ...