Suppress save events in Rails 5

Rails 5 added suppress method which is used to prevent the receiver from being saved during the given block.

Use case for suppress method

Let's say, we have an E-commerce application, which has many products. Whenever new product is launched then subscribed customers are notified about it.

class Product < ApplicationRecord
  has_many :notifications
  belongs_to :seller

  after_save :send_notification

  def launch!
    update_attributes!(launched: true)
  end

  private

  def send_notification
    notifications.create(message: 'New product Launched', seller: seller)
  end
end

class Notification < ApplicationRecord
  belongs_to :product
  belongs_to :seller

  after_create :send_notifications

  private

  def send_notifications
    # Sends notification about product to customers.
  end
end

class Seller < ApplicationRecord
  has_many :products
end

This creates a notification record every time we launch a product.

>> Notification.count
=> 0

>> seller = Seller.last
=> <Seller id: 6, name: "John">

>> product = seller.products.create(name: 'baseball hat')
=> <Product id: 4, name: "baseball hat", seller_id: 6>

>> product.launch!

>> Notification.count
=> 1

Now, we have a situation where we need to launch a product but we don't want to send notifications about it.

Before Rails 5, this was possible only by adding more conditions.

ActiveRecord::Base.Suppress in Rails 5

In Rails 5, we can use ActiveRecord::Base.suppress method to suppress creating of notifications as shown below.

class Product < ApplicationRecord
  def launch_without_notifications
    Notification.suppress do
      launch!
    end
  end
end

>> Notification.count
=> 0

>> product = Product.create!(name: 'tennis hat')
=> <Event id: 1, name: "tennis hat">

>> product.launch_without_notifications

>> Notification.count
=> 0

As we can see, no new notifications were created when product is launched inside Notification.suppress block.

Checkout the pull request to gain better understanding of how suppress works.