Now I hava a problem,how can I make the callback#after_add receive a reference to the join model in a has_many :through association?
my code like this:
class Emergency
has_many :departments, :through => :eme_references, :after_add => Proc.new { |eme_reference| eme_reference.eme_flag = 1}
end
the attribute eme_flag is the model EmeReference's attribute! but in the block ,i get the eme_reference.class is Emergency.
I want to set the attribute eme_flag of the model EmeReference.
That is my question!
cheers!
Presumably Emergency also has_many :eme_references in order for the :through association to work?
In that case, you should be able to attach the callback there:
has_many :eme_references,
:after_add => Proc.new { |emergency, eme_ref| # code here }
The block accepts 2 parameters, the first will be the Emergency, the 2nd will be the EmeReference being added.
Perhaps a before_save callback on EmeReference can also do what you want in this instance?
I think what you want to do can't be done there.
You could create an after_create hook on departments (I'm assuming Emergency has_many eme_references has_many departments):
class Emergency
has_many :departments, :through => :eme_references
def flag!
eme_flag=1
save
end
end
class Department
after_create :check_emergency
# this allows you to call department.emergency. Will return nil if anything is nil
delegate :emergency, :to =>:eme_reference, :allow_nil => true
def check_emergency
self.emergency.flag! if self.emergency.present?
end
end
Related
Have below association in author class
has_many :books,
class_name :"Learning::Books",
through: :elearning,
dependent: :destroy
with after_commit as,
after_commit :any_book_added?, on: :update
def any_book_added?
book = books.select { |book| book.previous_changes.key?('id') }
# book's previous_changes is always empty hash even when newly added
end
Unable to find the newly added association with this method. Is this due to class_name?
Rails has a couple methods that might help you, before_add and after_add
Using this, you can define a method to set an instance variable to true
class Author < ApplicationRecord
has_many :books, through: :elearning, after_add: :new_book_added
def any_book_added?
#new_book_added
end
private
def new_book_added
#new_book_added = true
end
end
Then when you add a book to an author, the new_book_added method will be called and you can at any future time ask your Author class if any_book_added?
i.e.
author = Author.last
author.any_book_added?
=> false
author.books = [Book.new]
author.any_book_added?
=> true
As you can see, the callback method new_book_added can accept the book that has been added as well so you can save that information.
I have the following models.
class Company < ApplicationRecord
has_many :company_users
has_many :users, :through => :company_users
after_update :do_something
private
def do_something
# check if users of the company have been updated here
end
end
class User < ApplicationRecord
has_many :company_users
has_many :companies, :through => :company_users
end
class CompanyUser < ApplicationRecord
belongs_to :company
belongs_to :user
end
Then I have these for the seeds:
Company.create :name => 'Company 1'
User.create [{:name => 'User1'}, {:name => 'User2'}, {:name => 'User3'}, {:name => 'User4'}]
Let's say I want to update Company 1 users, I will do the following:
Company.first.update :users => [User.first, User.second]
This will run as expected and will create 2 new records on CompanyUser model.
But what if I want to update again? Like running the following:
Company.first.update :users => [User.third, User.fourth]
This will destroy the first 2 records and will create another 2 records on CompanyUser model.
The thing is I have technically "updated" the Company model so how can I detect these changes using after_update method on Company model?
However, updating an attribute works just fine:
Company.first.update :name => 'New Company Name'
How can I make it work on associations too?
So far I have tried the following but no avail:
https://coderwall.com/p/xvpafa/rails-check-if-has_many-changed
Rails: if has_many relationship changed
Detecting changes in a rails has_many :through relationship
How to determine if association changed in ActiveRecord?
Rails 3 has_many changed?
There is a collection callbacks before_add, after_add on has_many relation.
class Project
has_many :developers, after_add: :evaluate_velocity
def evaluate_velocity(developer)
#non persisted developer
...
end
end
For more details: https://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#label-Association+callbacks
You can use attr_accessor for this and check if it changed.
class Company < ApplicationRecord
attr_accessor :user_ids_attribute
has_many :company_users
has_many :users, through: :company_users
after_initialize :assign_attribute
after_update :check_users
private
def assign_attribute
self.user_ids_attribute = user_ids
end
def check_users
old_value = user_ids_attribute
assign_attribute
puts 'Association was changed' unless old_value == user_ids_attribute
end
end
Now after association changed you will see message in console.
You can change puts to any other method.
I have the feelings you are asking the wrong question, because you can't update your association without destroy current associations. As you said:
This will destroy the first 2 records and will create another 2 records on CompanyUser model.
Knowing that I will advice you to try the following code:
Company.first.users << User.third
In this way you will not override current associations.
If you want to add multiple records once try wrap them by [ ] Or ( ) not really sure which one to use.
You could find documentation here : https://guides.rubyonrails.org/association_basics.html#has-many-association-reference
Hope it will be helpful.
Edit:
Ok I thought it wasn't your real issue.
Maybe 2 solutions:
#1 Observer:
what I do it's an observer on your join table that have the responsability to "ping" your Company model each time a CompanyUser is changed.
gem rails-observers
Inside this observer call a service or whatever you like that will do what you want to do with the values
class CompanyUserObserver < ActiveRecord::Observer
def after_save(company_user)
user = company_user.user
company = company_user.company
...do what you want
end
def before_destroy(company_user)
...do what you want
end
end
You can user multiple callback in according your needs.
#2 Keep records:
It turn out what you need it keep records. Maybe you should considerate use a gem like PaperTrail or Audited to keep track of your changes.
Sorry for the confusion.
So I have this model relationships
class User
has_one :wallet, :foreign_key => :user_id
end
class Wallet
after_initialize :set_value
def set_value
# Whatever
end
end
And I'd like that when I do User.last.wallet, User.last.wallet.new gets called.
I could achieve this by creating another method in the User model:
def get_wallet
self.wallet||self.wallet.new
end
and call get_wallet when needed.
But can't I get this without this useless and dirty extra method?
Something like:
has_one :wallet, :foreign_key => :user_id #, :build_if_not_found => true
Gems like this one: https://github.com/febuiles/auto_build don't do what I want: they build Wallet after creating the User object instead of creating when User.last.wallet is called.
Thanks
You can try this:
class User
has_one :wallet, :foreign_key => :user_id
def wallet
super || build_wallet
end
end
You still need to add some extra code, but it will do exactly what you want without any additional calls.
Is there any way to halt saving of child before parent.
I am using accepts_nested_attributes_for with polymorphic association.
I used multiple options validates_presence_of :parent_id , validates_assoicated :parent but none are working.
For example, I do have a class
Class Person
include HasPhoneNumbers
..
end
module HasPhoneNumbers
def self.included(kclass)
kclass.has_many :phone_numbers, :as => :callable, :dependent => kclass == Person ? :destroy : :nullify
end
klass.accepts_nested_attributes_for :phone_numbers, :reject_if => lambda {|pn| pn.keys.any?{|k| k.to_sym != :id && pn[k].blank?} }
end
class PhoneNumber
belongs_to :callable, :polymorphic => true
end
So while saving person due to validation in person object, it was not saving. However, child(phone_number) was saving. So I need to restrict it to not save child(phone_number) before parent(person) saves.
I did try multiple options using validates_presence_of and validates_associated, but none are working for me.
#person = Person.new(params[:person])
ActiveRecord::Base.transaction do
person.save!
end
Wrapping your saves within a transaction should roll back the phone number save if the person fails validation.
Reference: ActiveRecord Transactions
Is there a way to override one of the methods provided by an ActiveRecord association?
Say for example I have the following typical polymorphic has_many :through association:
class Story < ActiveRecord::Base
has_many :taggings, :as => :taggable
has_many :tags, :through => :taggings, :order => :name
end
class Tag < ActiveRecord::Base
has_many :taggings, :dependent => :destroy
has_many :stories, :through => :taggings, :source => :taggable, :source_type => "Story"
end
As you probably know this adds a whole slew of associated methods to the Story model like tags, tags<<, tags=, tags.empty?, etc.
How do I go about overriding one of these methods? Specifically the tags<< method. It's pretty easy to override a normal class methods but I can't seem to find any information on how to override association methods. Doing something like
def tags<< *new_tags
#do stuff
end
produces a syntax error when it's called so it's obviously not that simple.
You can use block with has_many to extend your association with methods. See comment "Use a block to extend your associations" here.
Overriding existing methods also works, don't know whether it is a good idea however.
has_many :tags, :through => :taggings, :order => :name do
def << (value)
"overriden" #your code here
super value
end
end
If you want to access the model itself in Rails 3.2 you should use proxy_association.owner
Example:
class Author < ActiveRecord::Base
has_many :books do
def << (book)
proxy_association.owner.add_book(book)
end
end
def add_book (book)
# do your thing here.
end
end
See documentation
I think you wanted def tags.<<(*new_tags) for the signature, which should work, or the following which is equivalent and a bit cleaner if you need to override multiple methods.
class << tags
def <<(*new_tags)
# rawr!
end
end
You would have to define the tags method to return an object which has a << method.
You could do it like this, but I really wouldn't recommend it. You'd be much better off just adding a method to your model that does what you want than trying to replace something ActiveRecord uses.
This essentially runs the default tags method adds a << method to the resulting object and returns that object. This may be a bit resource intensive because it creates a new method every time you run it
def tags_with_append
collection = tags_without_append
def collection.<< (*arguments)
...
end
collection
end
# defines the method 'tags' by aliasing 'tags_with_append'
alias_method_chain :tags, :append
The method I use is to extend the association. You can see the way I handle 'quantity' attributes here: https://gist.github.com/1399762
It basically allows you to just do
has_many : tags, :through => : taggings, extend => QuantityAssociation
Without knowing exactly what your hoping to achieve by overriding the methods its difficult to know if you could do the same.
This may not be helpful in your case but could be useful for others looking into this.
Association Callbacks:
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html
Example from the docs:
class Project
has_and_belongs_to_many :developers, :after_add => :evaluate_velocity
def evaluate_velocity(developer)
...
end
end
Also see Association Extensions:
class Account < ActiveRecord::Base
has_many :people do
def find_or_create_by_name(name)
first_name, last_name = name.split(" ", 2)
find_or_create_by_first_name_and_last_name(first_name, last_name)
end
end
end
person = Account.first.people.find_or_create_by_name("David Heinemeier Hansson")
person.first_name # => "David"
person.last_name # => "Heinemeier Hansson"
Rails guides documents about overriding the added methods directly.
OP's issue with overriding << probably is the only exception to this, for which follow the top answer. But it wouldn't work for has_one's = assignment method or getter methods.