CODEWITHSUNDEEP
ruby-on-railsmodelattributes
Andre Zimpel
Andre Zimpel

Reputation: 2343

Rails model callback (after create/update) attribute_was not working

I am migrating a rails 5.1 app to rails 5.2.1. In my models I am using callbacks to create an activity log after a model was created or updated. Unfortunately todo.name and todo.name_was is always the same - the current value. This applies to every attribute and every model. Also changed? returns false.

Am I missing something?

I appreciate your help a lot!

Upvotes: 5

Views: 7485

Answers (2)

Nimish Gupta
Nimish Gupta

Reputation: 3175

You won't get attribute_was in after_create/update callback as the records has been changed in DB at this point.

You can make use of previous_changes in after_create/update callbacks.

Here is an example below.

Consider, User Model:

class User < ApplicationRecord

  before_update :check_for_changes
  after_update :check_for_previous_changes

  private def check_for_changes
    puts changes # => {"name"=>["Nimish Gupta", "Nimish Mahajan"], "updated_at"=>[Tue, 20 Nov 2018 00:02:14 PST -08:00, Tue, 20 Nov 2018 00:06:15 PST -08:00]}
    puts previous_changes # => {} At this point this will be empty beacuse changes are not made to DB yet
    puts name_was # => "Nimish Gupta" i.e the original name
    puts name # => "Nimish Mahajan" i.e the new name which will be going to save in DB
  end

  private def check_for_previous_changes
    puts changes # => {}
    # Please note `changes` would be empty now because record have been saved in DB now

    # but you can make use of previous_changes method to know what change has occurred.
    puts previous_changes # => {"name"=>["Nimish Gupta", "Nimish Mahajan"], "updated_at"=>[Tue, 20 Nov 2018 00:06:15 PST -08:00, Tue, 20 Nov 2018 00:08:07 PST -08:00]}

    puts name_was # => "Nimish Mahajan" i.e the new name which have been saved in DB
    puts name # => "Nimish Mahajan" i.e the new name which have been saved in DB

    # to get the previous name if after_create/update callback, Please use.
    puts previous_changes[:name][0]
  end

end

u = User.first # => #<User id: 1, name: "Nimish Gupta">
u.update(name: 'Nimish Mahajan') # => this will fire both before_update and after_update callbacks.

Hope this will help you.

You can also take a look at this answer for more information

Upvotes: 13

Pramod Shinde
Pramod Shinde

Reputation: 1892

I think you are using changed? on a persisted objet, attribute_was, changed? only works when object is dirty see for more details https://api.rubyonrails.org/classes/ActiveModel/Dirty.html

class Todo < ApplicationRecord 
end
todo = Todo.new
todo.changed? # => false
todo.persisted? # => false

If you save the object in DB the object becomes persisted(no more dirty data present)

todo = Todo.new(name: 'Test') 
todo.name_was # => nil
todo.name_changed? #=> true
todo.save
todo.persisted? # => true
todo.name_was # => Test
todo.name_changed? #=> false

Upvotes: 4

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