Rails 6 adds ActiveRecord::Relation#extract_associated

Before Rails 6, if we want to extract associated records from an ActiveRecord::Relation, we would use preload and collect.

For example, we want to fetch subscriptions of some users. The query would look as shown below.

Rails 5.2

User.where(blocked: false).preload(:subscriptions).collect(&:subscriptions)

=> # returns collection of subscription records

ActiveRecord::Relation#extract_associated provides a shorthand to achieve same result and is more readable than former.

Rails 6.0.0.beta3

User.where(blocked: false).extract_associated(:subscriptions)

=> # returns the same collection of subscription records

Here's the relevant pull request for this change.