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The lib folder and its use cases

The only cases where we should use the lib folder are in these cases:

  • Overriding 3rd party library specifics or modules.

  • Overriding String class from Ruby.

  • For keeping logic shared by controllers, models as well as say configs or even Rake tasks.

  • The lib folder was used a lot in old Rails where all helpers were used to be written in this folder.

Why prefer carriers over view helpers

You can refer to this BigBinary blog to learn about carriers and why carriers are preferred over view helpers.


We already discussed about some of the dirty methods while we had added slug to tasks. Documenting all of the dirty methods will be pretty much replicating the whole Rails docs. Thus here are few of the useful dirty methods:


Returns the change to an attribute during the last save. If the attribute was changed, the result will be an array containing the original value and the saved value.

This method is useful in after callbacks, to see the change in an attribute during the save that triggered the callbacks to run. It can be invoked as saved_change_to_name instead of saved_change_to_attribute("name").

Another real world example would be when we have to deactivate users from a team if the team's subscription payment has failed. Let's say payment_status is an ENUM field which stores the payment statuses. Thus we could add a concern like so:

1# frozen_string_literal: true
3module AccountDeactivation
4  extend ActiveSupport::Concern
6  included do
7    after_update do
8      if payment_failed?
9        deactivate_team_members!
10      end
11    end
12  end
14  private
16    def payment_failed?
17      self.saved_change_to_payment_status&.last == "failed"
18    end
20    def deactivate_team_members!
21      self.subscribers.deactivate!
22    end

We could include this concern in say our Team model and take care of the deactivation with ease.


You can read more about ActionText from the official documentation.


You can read more about ActionCable from the official documentation.

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