Im creating an object (recipe_change) that has many ingredient_changes. However I want to run my own validation of sort and prevent the creation of ingredient_changes if they dont pass. I started with a validation in the ingredient_changes but with that if I added an error the valid? would prevent the change from being submitted if one of the many ingredient_changes wasnt valid...which I dont want. So then I tried the following in my create method in the recipe_change controller and this almost did the job except once it deleted one it would break the loop and not do the rest:
#recipe_change.ingredient_changes.each do |change|
if ...long conditional statement...
#recipe_change.ingredient_changes.delete(change)
end
end
Is there a function like the array .reject! that works for associations like this. At this point in the code they are not saved to the database and Im trying to not save them to the database if they dont meet my condition.
You can use reject_if to filter out invalid ingredient_changes in recipe_change model like this:
class RecipeChange < ActiveRecord::Base
has_many :ingredient_changes, reject_if: :invalid_ingredient_change?
def invalid_ingredient_change?(attributes)
end
end
See: http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html
Related
I would like to implement certain relationship between 2 models.
I have 2 models: quiz and question that have many-to-many relationship.
Quiz model have quiz_flag and question model have question_flag.
What I want to happen is when quiz_flag is changed to true, every question that is in direct relationship (basically every question that is contained within that quiz), should also change question_flag to true.
Logic is similar to dependent: :destroy, but it's a custom function that I want to trigger when quiz_flag becomes true.
But how do I specifically do that?
You could just add additional logic to whatever form/action is responsible for setting quiz.
I.e.:
if params[:quiz_flag] #if the quiz_flag params is set to true.
#quiz.questions.update_all(question_flag: true)
end
Or if it's for multiple controllers, you could use callbacks:
Quiz Model:
before_save :some_method #will work before object is saved
(works with both create and update, if you just want update use before_update)
def some method
if self.quiz_flag == true
self.questons.update_all(question_flag:true)
end
end
I would caution you on using callbacks though. It can lead to some messy code that will be difficult to test for later.
You can use the callback :before_update inside your model.
I'd do something like this:
class Quiz < ApplicationRecord
before_update :update_question_flags, :if => :question_flag_changed?
def update_question_flags
self.questons.update_all(question_flag:true)
end
end
I am adding a feature to an old app that was not made by me, this along with being relatively new to RoR is leading to some confusion for me.
I have models called reponse, activity_point, and report
response has two parents, it belongs_to activity_point and report.
I am trying to access activity_points for a do block like so:
report.responses.activity_points.activity.each do |a|
Obviously that isn't working. I am getting the error message:
undefined method `activity_points' for []:ActiveRecord::Relation
Thanks to anyone who can help me with this little problem.
Or you can add something like this to your Report model
has_many :responses
has_many :activity_points, :through => :responses
has_many :activities, :through => :activity_points
then you can do this
report.activities.each do |a|
Another way to do this kind of thing, add a method to Report and joins from the other side (to get activity objects)
def activities
Activity.joins(:activity_points => :responses).where('responses.report_id = ?', id)
end
The point of doing all this, you don't want to create Ruby objects if you don't need to. Nested loops are also a potential problem with unique items and sorting.
Each response have several activity_points so you should iterate through responses. Also each activity_point has several activities, so:
report.responses.each do |r|
r.activity_points.each do |ap|
ap.activity.each do |a|
# Do your thing
end
end
end
First, when you write report.responses, this will return an ActiveRecord array. Since activity_points is an undefined method for arrays, you can't call it. So to call this method there is two conditions:
You have to tell your app which element of the array will call the method. For instance, report.responses.first.activity_points or report.responses.second.activity_points ...
Response model has to have a has_many: activity_points to call this method.
You could still also use a loop, but that will take multiple DB calls. Therefore, my solution involves direct database call for efficiency.
Activity.includes(activity_point: {responses: :report}).where(reports: {id: report.id}).each do |a|
#...
#...
end
I want to preview what the model will look like when saved without currently saving to the database.
I am using #event.attributes = because that assigns but does not save attributes for #event to the database.
However, when I also try to assign the audiences association, Rails inserts new records into the audiences_events join table. Not cool. Is there a way to preview what these new associations will look like without inserting into the join table?
Model
class Event < ActiveRecord::Base
has_and_belongs_to_many :audiences # And vice versa for the Audience model.
end
Controller
class EventsController < ApplicationController
def preview
#event = Event.find(params[:id])
#event.attributes = event_params
end
private
def event_params
params[:event].permit(:name, :start_time, :audiences => [:id, :name]
end
end
Possible Solutions?
Possible solutions that I thought of, but don't know how to do:
Using some sort of method that assigns associations, but does not persist them.
disabling all database writes for this one action (I dont know how to do that).
Rolling back all database changes at the end of this action
Any help with these would be great!
UPDATE:
After the reading the great answers below, I ended up writing this service class that assigns the non-nested attributes to the Event model, then calls collection.build on each of the nested params. I made a little gist. Happy to receive comments/suggestions.
https://gist.github.com/jameskerr/69cedb2f30c95342f64a
In these docs you have:
When are Objects Saved?
When you assign an object to a has_and_belongs_to_many association, that object is automatically saved (in order to update the join table). If you assign multiple objects in one statement, then they are all saved.
If you want to assign an object to a has_and_belongs_to_many association without saving the object, use the collection.build method.
Here is a good answer for Rails 3 that goes over some of the same issues
Rails 3 has_and_belongs_to_many association: how to assign related objects without saving them to the database
Transactions
Creating transactions is pretty straight forward:
Event.transaction do
#event.audiences.create!
#event.audiences.first.destroy!
end
Or
#event.transaction do
#event.audiences.create!
#event.audiences.first.destroy!
end
Notice the use of the "bang" methods create! and destroy!, unlike create which returns false create! will raise an exception if it fails and cause the transaction to rollback.
You can also manually trigger a rollback anywhere in the a transaction by raising ActiveRecord::Rollback.
Build
build instantiates a new related object without saving.
event = Event.new(name: 'Party').audiences.build(name: 'Party People')
event.save # saves both event and audiences
I know that this is a pretty old question, but I found a solution that works perfectly for me and hope it could save time to someone else:
class A
has_many :bs, class_name 'B'
end
class B
belongs_to :a, class_name: 'A'
end
a.bs.target.clear
new_bs.each {|new_b| a.bs.build new_b.attributes.except('created_at', 'updated_at', 'id') }
you will avoid autosave that Rails does when you do a.bs = new_bs
I am having a very strange problem in Rails. I am using update_attributes on a Parent Object to update all the children objects. The children objects have (custom) validation and indeed this works ok, meaning that if I give wrong values the validation trigger and I get an error back.
Now I am in a strange situation where one of the model is invalid in the database (let's not question why, let's just say I can go in the DB and run some SQL to make the model invalid). If I go in my app I can see the invalid values and this is fine. I fix the values and save again and I can see, stepping in the ruby code that the validation is called also BEFORE saving the new values, meaning that I will get an error and Rails will never execute the SQL to actually update the values to the correct ones.
I hope the above makes sense. Do you have any idea or do you think there is something I am overlooking?
SOLUTION:
What was happening was that a many-to-many relationship was validating the existing DB data before being replaced by the new data. Basically the structure was like this:
class User
has_many :user_permissions
has_many :permissions, :through => :model_permissions
class Permission
has_many :user_permissions
has_many :users, :through => :user_permissions
class UserPermission
belongs_to :user
belongs_to :permission
validates_associated :user # THIS was causing the problem
validates_associated :permission # and THIS as well
I simply removed the validates_associated directive, since I am validating the linked records independently anyway.
Well, Rails does run your validation prior to writing the data to the database (please refer to Active Record callback sequence), so having validation errors means that some piece of the model you are trying to save is not valid. It might an associated model containing errors with the validation turned on or just some missing part – in any case, just have a look at what are the errors you are getting.
In case (let's no question why either :) you want to skip validation - you are open to choose from #update_attribute (to update just one attribute), calling #save(false), using +udpate_all method of the model class or even go down to ActiveRecord::Base.connection.execute – none of these will ever bother you with validation errors :)
Updated
Appears to be a precedence error and nothing to do with the question I originally asked. See discussion below.
Original question
Is it possible to use active record associations in callbacks? I've tested this code in the console and it works fine as long as it isn't in a callback. I'm trying to create callbacks that pull attributes from other associated models and I keep getting errors of nil.attribute.
If callbacks are not the correct approach to take, how would one do a similar action in rails? If the associations are simple, you could use create_association(attributes => ), but as associations get more complex this starts to get messy.
For example...
class User < ActiveRecord::Base
belongs_to :b
before_validation_on_create {|user| user.create_b} #note, other logic prevents creating multiple b
end
class B < ActiveRecord::Base
has_many :users, :dependent => destroy
after_create{ |b| b.create_c }
has_one :c
end
class C < ActiveRecord::Base
belongs_to :b
after_create :create_alert_email
private
def create_alert_email
self.alert_email = User.find_by_b_id(self.b_id).email #error, looks for nil.email
end
end
Off course associations are available in your callbacks. After all, the create_after_email is simply a method. You can even call it alone, without using a callback. ActiveRecord doesn't apply any special flag to callback methods to prevent them from working as any other method.
Also notice you are running a User#find query directly without taking advantage of any association method. An other reason why ActiveRecord association feature should not be the guilty in this case.
The reason why you are getting the error should probably searched somewhere else.
Be sure self.b_id is set and references a valid record. Perhaps it is nil or actually there's no User record with that value. In fact, you don't test whether the query returns a record or nil: you are assuming a record with that value always exists. Are you sure this assumption is always statisfied?