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New Rails 7 features, Before and After
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rails7_before_after.md

Add ComparisonValidator

Before Rails 7

class Event < ApplicationRecord
  validates :start_date, presence: true
  validates :end_date, presence: true

  validate :end_date_is_after_start_date

  private

  def end_date_is_after_start_date
    if end_date < start_date
      errors.add(:end_date, 'cannot be before the start date')
    end
  end
end

After Rails 7

class Event < ApplicationRecord
  validates :start_date, presence: true
  validates :end_date, presence: true
  
  validates_comparison_of :end_date, greater_than: :start_date
end

Disable partial_inserts as default

# == Schema Information
#
# Table name: posts
#
#  id                     :bigint
#  title                  :string
#  description            :text
#  created_at             :datetime
#  updated_at             :datetime

class Post < ApplicationRecord
end

Before

It's enabled as default

Rails.configuration.active_record.partial_inserts => true

The INSERT command does not include description as we are just passing title to the Post.new command

> Post.new(title: 'Rails 7').save

Post Create (1.7ms)  INSERT INTO "posts" ("title", "created_at", "updated_at") VALUES (?, ?, ?)  [["title", "Rails 7"], ["created_at", "2021-12-25 20:31:01.420712"], ["updated_at", "2021-12-25 20:31:01.420712"]]

After

It's disabled as default

Rails.configuration.active_record.partial_inserts => false

The INSERT command includes description too, even when we don't pass description to the Post.new command

> Post.new(title: 'Rails 7').save

Post Create (1.7ms)  INSERT INTO "posts" ("title", "description", "created_at", "updated_at") VALUES (?, ?, ?)  [["title", "Rails 7"], ["description", ""], ["created_at", "2021-12-25 20:31:01.420712"], ["updated_at", "2021-12-25 20:31:01.420712"]]

Add tracking of belongs_to association

class Event
  belongs_to :organizer
end

class Organizer
  has_many :events
end

association_changed? method

The association_changed? method tells if a different associated object has been assigned and the foreign key will be updated in the next save.

Before

Tracking the target of a belongs_to association was able by checking its foreign key.

class Event
  belongs_to :organizer
  before_save :track_change
    
  private
    
  def track_change
    if organizer_id_changed?
      #track something
    end
  end
end

After

It's doable by using association_changed? method

class Event
  belongs_to :organizer
  before_save :track_change
    
  private
    
  def track_change
    if organizer_changed?
      #track something
    end
  end
end

association_previously_changed? method

The association_previously_changed? method tells if the previous save updated the association to reference a different associated object.

> event.organizer
=> #<Organizer id: 1, name: "Organization 1">

> event.organizer = Organizer.second
=> #<Organizer id: 2, name: "Organization 2">

> event.organizer_changed?
=> true

> event.organizer_previously_changed?
=> false

> event.save!
=> true

> event.organizer_changed?
=> false

> event.organizer_previously_changed?
=> true

Add invert_where method

Allows you to invert an entire where clause instead of manually applying conditions.

class User
  scope :active, -> { where(accepted: true, locked: false) }
end

Before

active_users = User.active
inactive_users = User.where.not(id: User.active.ids)

After

active_users = User.active
inactive_users = User.active.invert_where

More examples: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-invert_where Side effects of invert_where: https://blog.kiprosh.com/side-effects-of-activerecords-new-feature-invert_where-in-rails-7/

Active Record Encryption

without encryption

> Post.create(title: 'Rails 7')

INSERT INTO "posts" ("title") VALUES (?)  [["title", "Rails 7"]]

Encryption Before

We had to write a lot of extra codes, and use a gem (e.g. https://github.com/attr-encrypted/attr_encrypted) or play with ActiveSupport::MessageEncryptor (tutorial here: https://pawelurbanek.com/rails-secure-encrypt-decrypt)

After

class Post < ApplicationRecord
  encrypts :title
end
> Post.create(title: 'Rails 7')

INSERT INTO `posts` (`title`) VALUES ('{\"p\":\"n7J0/ol+a7DRMeaE\",\"h\":{\"iv\":\"DXZMDWUKfp3bg/Yu\",\"at\":\"X1/YjMHbHD4talgF9dt61A==\"}}')

Querying non-deterministically encrypted data is impossible:

> Post.find_by title: 'Rails 7'
# => nil

If you want to directly query an encrypted column attribute, you'd need to use the deterministic approach. For this, simply use the deterministic: true option during declaration.

class Post < ApplicationRecord
  encrypts :title, deterministic: true
end
> Post.create(title: 'Rails 7')
INSERT INTO `posts` (`title`) VALUES ('{\"p\":\"n7J0/ol+a7DRMeaE\",\"h\":{\"iv\":\"DXZMDWUKfp3bg/Yu\",\"at\":\"X1/YjMHbHD4talgF9dt61A==\"}}')

> Post.find_by title: 'Rails 7'
# => <Post:0x00 id: 1, title: "Rails 7"...>

PostgreSQL generated columns

Before

One of the options was using callbacks:

# == Schema Information
#
# Table name: prders
#
#  id                     :bigint
#  price                  :decimal, precision: 8, scale: 2
#  tax                    :decimal, precision: 8, scale: 2
#  total                  :decimal, precision: 8, scale: 2
#  created_at             :datetime
#  updated_at             :datetime

class Order < ApplicationRecord
  before_save :calculate_total
  
private

  def calculate_total
    self[:total] = price + tax
  end
end

Result:

order = Order.create!(price: 12, tax: 1)
order.total => 13

After

You just need to use virtual and all will be done automatically by postgres

create_table :orders, force: true do |t|
  t.decimal :price, precision: 8, scale: 2
  t.decimal :tax, precision: 8, scale: 2
  t.virtual :total, type: :decimal, as: 'price + tax', stored: true
end

Result: You need to reload data to get the calculated value form the DB

order = Order.create!(price: 12, tax: 1)
order.total => nil

order.reload
order.total => 13
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