---
title: 'This week in #dev (Apr 21, 2023)'
teaser: 'This week, we discussed splitting arrays, handling deprecation warnings,
  and querying missing records.

  '
tags: this week in dev,til,rails,ruby
author: thoughtbot
published_on: 2023-05-01
---

Welcome to another edition of This Week in #dev, a series of posts where we
bring some of the most interesting Slack conversations to the public. Today
we're talking about: splitting arrays, handling deprecation warnings, and
querying missing records.

## A Handy Method for Splitting Enumerables

[Steve Polito] learned about [Ruby's `Enumerable#partition`]. This method is useful for
dividing an existing array into two separate arrays, he says.

```rb
# Before
def call(appointments)
  appointments_today = []
  appointments_next_week = []
​
  appointments.each do |appointment|
    if appointment.starts_at.to_date == Date.current
      appointments_today << appointment
    else
      appointments_next_week << appointment
    end
  end
end
​
# After
def call(appointments)
  appointments_today, appointments_next_week = appointments.partition do |appointment|
    appointment.starts_at.to_date == Date.current
  end
end
```

[Ruby's `Enumerable#partition`]: https://rubyapi.org/3.2/o/enumerable#method-i-partition

## Handling Ruby Deprecation Warnings

[Neil Carvalho] discovers that Ruby deprecation warnings have been disabled
[since Ruby 2.7.2] due to an excessive number of deprecation warnings related to
keyword arguments. This concerns him, and he suggests setting
`Warning[:deprecated]` to `true` in `spec_helper.rb` and asks for other
suggestions.

[Summer ☀️] steps in and proposes logging warnings to an error-tracking service
in production, while in development and testing, they recommend raising errors
instead of relying on log messages that can be easily overlooked. It would be
also important to be able to choose whether these actions apply to project code
or dependencies, and selectively silence specific deprecation types or downgrade
them from errors to warnings.

<aside class="info">
  <p>
    <a href="https://thoughtbot.com/blog/authors/summer">Summer ☀️</a> mentions the
    usefulness of Shopify’s
    <a href="https://github.com/Shopify/deprecation_toolkit">deprecation_toolkit</a>,
    which offers these functionalities for both <code>Warning</code> and
    <code>ActiveSupport::Deprecation</code>.
  </p>
</aside>

[since Ruby 2.7.2]: https://bugs.ruby-lang.org/issues/16345

## Querying Missing Associated Records

[Rémy Hannequin] seeks assistance with an ActiveRecord query to retrieve records
that are missing associated records with a specific attribute. He provides an
example scenario of authors and books with different languages and wants to find
authors who don't have books written in Elvish:

```rb
# This is not what Remy wants
Author
  .where.missing(:books)
  .where(books: {language: :elvish})

# That generates this SQL
SELECT * FROM "authors"
LEFT OUTER JOIN "books" ON "books"."author_id" = "authors"."id"
WHERE "books"."id" IS NULL
AND "books"."language" = "elvish"
```

Neil Carvalho responds with two possible approaches. If it makes sense to define
a specific association for Elvish books in the `Author` model, Neil Carvalho
suggests using `Author.where.missing(:elvish_books)` to query authors without
associated Elvish books.

```rb
class Author
  has_many :elvish_books, -> { where(language: "elvish") }, class_name: "Book"
end

# Now this works!
Author.where.missing(:elvish_books)
```

If it doesn't make sense to define a separate association, the recommendation is
using a left join:

```rb
Author.left_joins('books ON books.author_id = authors.id AND books.language = "elvish"')
```

## Thanks

This edition was brought to you by [Neil Carvalho], [Rémy Hannequin], [Steve Polito], and [Summer ☀️].
Thanks to all contributors! 🎉

[neil carvalho]: https://thoughtbot.com/blog/authors/neil-carvalho
[steve polito]: https://thoughtbot.com/blog/authors/steve-polito
[Summer ☀️]: https://thoughtbot.com/blog/authors/summer
[rémy hannequin]: https://thoughtbot.com/blog/authors/remy-hannequin