I have two models:
class Basket < ActiveRecord::Base
has_many :products
def recalculate_price!
price = products.map(&:price).sum
save
end
end
class Product < ActiveRecord::Base
belongs_to :basket
after_save :update_basket
def update_basket
basket.recalculate_price!
end
end
and than I call it like this:
basket = Basket.new
basket.products.build(price)
basket.save
The problem: basket.price don't update.
I've investigated the problem and found out that there is some kind of caching in update_basket method. The problem could be solved with placing reload before basket.recalculate_price!.
Is there any option to leave the update_basket method untouched? I have many such cases in my application.
I would like to understand how it works and avoid similar problems in the future.
note: I recently upgraded rails from 3.2 to 4.2. In a previous version everything worked fine.
Is there any option to leave the update_basket method untouched?
Absolutely. You can place a condition on your after_create to avoid executing it some times:
after_save :update_basket if: :basked_should_be_updated
[...]
private
def basked_should_be_updated
[...]
# return true or false in here
end
Related
Let's say I have a model Checklist that has_many :items and accepts_nested_attributes_for :items.
I want to know in some Item callbacks and validations if it is being updated via nested attributes or just on its own. (This can e.g. let me optimise by running certain hooks only once when multiple Items are edited via the Checklist.)
How can I detect this?
I found what seems like a pretty good way.
I add a flag to Item, and override Checklist items_attributes= to set that flag.
Item:
class Item < ApplicationRecord
# …
attr_accessor :updated_via_checklist
after_save do
if updated_via_checklist
# Do nothing. The Checklist does something in batch.
else
do_something_for_just_this_item
end
end
end
Checklist:
class Checklist < ApplicationRecord
# …
after_save do
do_something_in_batch(items)
end
def items_attributes=(value)
return_value = super
items.each { _1.updated_via_checklist = true }
return_value
end
end
You can detect if an object is being updated via nested attributes by checking the object's _nested_attributes flag
https://guides.rubyonrails.org/v6.1/2_3_release_notes.html#nested-attributes
Or just a couple of lines shorter:
# checklist.rb
def items_attributes=(value)
super(value.merge!({updated_via_checklist: true}))
end
Is there a callback for active storage files on a model
after_update or after_save is getting called when a field on the model is changed. However when you update (or rather upload a new file) no callback seems to be called?
context:
class Person < ApplicationRecord
#name :string
has_one_attached :id_document
after_update :call_some_service
def call_some_service
#do something
end
end
When a new id_document is uploaded after_update is not called however when the name of the person is changed the after_update callback is executed
For now, it seems like there is no callback for this case.
What you could do is create a model to handle the creation of an active storage attachment which is what is created when you attach a file to your person model.
So create a new model
class ActiveStorageAttachment < ActiveRecord::Base
after_update :after_update
private
def after_update
if record_type == 'Person'
record.do_something
end
end
end
You normally have created the model table already in your database so no need for a migration, just create this model
Erm i would just comment but since this is not possible without rep..
Uelb's answer works but you need to fix the error in comments and add it as an initializer instead of model. Eg:
require 'active_storage/attachment'
class ActiveStorage::Attachment
before_save :do_something
def do_something
puts 'yeah!'
end
end
In my case tracking attachment timestamp worked
class Person < ApplicationRecord
has_one_attached :id_document
after_save do
if id_document.attached? && (Time.now - id_document.attachment.created_at)<5
Rails.logger.info "id_document change detected"
end
end
end
The answer from #Uleb got me 90% of the way, but for completion sake I will post my final solution.
The issue I had was that I was not able to monkey patch the class (not sure why, even requiring the class as per #user10692737 did not help)
So I copied the source code (https://github.com/rails/rails/blob/fc5dd0b85189811062c85520fd70de8389b55aeb/activestorage/app/models/active_storage/attachment.rb#L20)
and modified it to include the callback
require "active_support/core_ext/module/delegation"
# Attachments associate records with blobs. Usually that's a one record-many blobs relationship,
# but it is possible to associate many different records with the same blob. If you're doing that,
# you'll want to declare with <tt>has_one/many_attached :thingy, dependent: false</tt>, so that destroying
# any one record won't destroy the blob as well. (Then you'll need to do your own garbage collecting, though).
class ActiveStorage::Attachment < ActiveRecord::Base
self.table_name = "active_storage_attachments"
belongs_to :record, polymorphic: true, touch: true
belongs_to :blob, class_name: "ActiveStorage::Blob"
delegate_missing_to :blob
#CUSTOMIZED AT THE END:
after_create_commit :analyze_blob_later, :identify_blob, :do_something
# Synchronously purges the blob (deletes it from the configured service) and destroys the attachment.
def purge
blob.purge
destroy
end
# Destroys the attachment and asynchronously purges the blob (deletes it from the configured service).
def purge_later
blob.purge_later
destroy
end
private
def identify_blob
blob.identify
end
def analyze_blob_later
blob.analyze_later unless blob.analyzed?
end
#CUSTOMIZED:
def do_something
end
end
Not sure its the best method, and will update if I find a better solution
None of these really hit the nail on the head, but you can achieve what you were looking for by following this blog post https://redgreen.no/2021/01/25/active-storage-callbacks.html
I was able to modify the code there to work on attachments instead of blobs like this
Rails.configuration.to_prepare do
module ActiveStorage::Attachment::Callbacks
# Gives us some convenient shortcuts, like `prepended`
extend ActiveSupport::Concern
# When prepended into a class, define our callback
prepended do
after_commit :attachment_changed, on: %i[create update]
end
# callback method
def attachment_changed
record.after_attachment_update(self) if record.respond_to? :after_attachment_update
end
end
# After defining the module, call on ActiveStorage::Blob to prepend it in.
ActiveStorage::Attachment.prepend ActiveStorage::Attachment::Callbacks
end
What I do is add a callback on my record:
after_touch :check_after_touch_data
This gets called if an ActiveStorage object is added, edited or deleted. I use this callback to check if something changed.
I have a model that uses rails' built-in counter_cache association to increment/decrement counts. I have a requirement wherein I need to disable this when I destroy the model for a specific situation. I have tried to do something like Model.skip_callback(:destroy, :belongs_to_counter_cache_after_update) but it doesn't seem to work as expected (i.e it still ends up decrementing the associated model). Any helpful pointers would be appreciated.
One option is to temporarily override the method responsible for updating the cache count in case of destroy.
For example if you have following two models
class Category < ActiveRecord::Base
has_many :products
end
class Product < ActiveRecord::Base
belongs_to :category, counter_cache: true
end
Now you can try to find the methods responsible for updating cache count with following
2.1.5 :038 > Product.new.methods.map(&:to_s).grep(/counter_cache/)
This shows all the product instance methods which are related to counter_cache, with following results
=> ["belongs_to_counter_cache_before_destroy_for_category", "belongs_to_counter_cache_after_create_for_category", "belongs_to_counter_cache_after_update_for_category"]
From the names of the methods it shows that
"belongs_to_counter_cache_after_create_for_category"
might be responsible for counter cache update after destroy.
So I decided to temporarily override this method with one fake method which doesn't do anything(to skip counter cache update)
Product.class_eval do
def fake_belongs_to_counter_cache_before_destroy_for_category; end
alias_method :real_belongs_to_counter_cache_before_destroy_for_category, :belongs_to_counter_cache_before_destroy_for_category
alias_method :belongs_to_counter_cache_before_destroy_for_category, :fake_belongs_to_counter_cache_before_destroy_for_category
end
Now if you will destroy any product object, it will not update counter cache in Category table.
But its very important to restore the actual method after you have run your code to destroy specific objects. To restore to actual class methods you can do following
Product.class_eval do
alias_method :belongs_to_counter_cache_before_destroy_for_category, :real_belongs_to_counter_cache_before_destroy_for_category
remove_method :real_belongs_to_counter_cache_before_destroy_for_category
remove_method :fake_belongs_to_counter_cache_before_destroy_for_category
end
To ensure that the methods definitions always restored after your specific destroy tasks, you can write a class method, that will make sure to run both override and restore code
class Product < ActiveRecord::Base
belongs_to :category, counter_cache: true
def self.without_counter_cache_update_on_destroy(&block)
self.class_eval do
def fake_belongs_to_counter_cache_before_destroy_for_category; end
alias_method :real_belongs_to_counter_cache_before_destroy_for_category, :belongs_to_counter_cache_before_destroy_for_category
alias_method :belongs_to_counter_cache_before_destroy_for_category, :fake_belongs_to_counter_cache_before_destroy_for_category
end
yield
self.class_eval do
alias_method :belongs_to_counter_cache_before_destroy_for_category, :real_belongs_to_counter_cache_before_destroy_for_category
remove_method :real_belongs_to_counter_cache_before_destroy_for_category
remove_method :fake_belongs_to_counter_cache_before_destroy_for_category
end
end
end
Now if you destroy any product object as given following
Product.without_counter_cache_update_on_destroy { Product.last.destroy }
it will not update the counter cache in Category table.
References:
Disabling ActiveModel callbacks https://jeffkreeftmeijer.com/2010/disabling-activemodel-callbacks/
Temporary overriding methods: https://gist.github.com/aeden/1069124
You can create a flag to decide when callback should be run, something like:
class YourModel
attr_accessor :skip_counter_cache_update
def decrement_callback
return if #skip_counter_cache_update
# Run callback to decrement counter cache
...
end
end
so before you destroy your object of a Model, just set value for skip_counter_cache_update:
#object = YourModel.find(some_id)
#object.skip_counter_cache_update = true
#object.destroy
so it will not run decrement callback.
I'm using Rails 5. I want a method invoked on my model only when the model is first created. I have tried this ...
class UserSubscription < ApplicationRecord
belongs_to :user
belongs_to :scenario
def self.find_active_subscriptions_by_user(user)
UserSubscription.joins(:scenario)
.where(["user_id = ? and start_date < NOW() and end_date > NOW()", user.id])
end
after_initialize do |user_subscription|
self.consumer_key = SecureRandom.urlsafe_base64(10)
self.consumer_secret = SecureRandom.urlsafe_base64(25)
end
end
but I noticed this gets called every tiem I retrieve a model from a finder method in addition to its begin created. How can I create such functionality in my model?
You want to use after_create (from active record docs) or after_create_commit which was introduced in Rails 5 as a shortcut for after_commit :hook, on: :create.
after_create always executes after the transactions block whereas after_create_commit does so after the commit but within the same transactions block. These details likely don't matter here, but it's a new capability if you need that extra control for ensuring the model state is correct before you execute the after call.
Pyrce's answer is good. Another way is to keep the after_initialize method but only run if it's a new record:
after_initialize :set_defaults
def set_defaults
if self.new_record?
self.consumer_key = SecureRandom.urlsafe_base64(10)
self.consumer_secret = SecureRandom.urlsafe_base64(25)
end
end
(It's generally considered better to not override the after_initialize method. Instead provide the name of a method to run, as I did above.
Is it possible to have a 'before_save' callback that detects if a 'has_one' relationship has changed (the relationship not the model at the end of the relationship)? For example, something that would act like this:
#person.picture = #picture
#person.picture_changed? # true
#person.save
#person.picture_changed? # false
Maybe it works with
#person.picture_id_changed?
Try relation.changed?... You may also want to look into observers, depending on what you are trying to accomblish.
Example:
class Model < ActiveRecord::Base
has_one :relation
before_save :check_relation_changed
private def check_relation_changed
do_something if relation.changed?
end
end
Ref: http://ryandaigle.com/articles/2008/3/31/what-s-new-in-edge-rails-dirty-objects