Howto use callbacks in a has_many through association?
has_many :through rails
belongs to many rails
I have a Task model associated to a Project model via has_many through and need to manipulate the data before delete/insert via the association.
Since "Automatic deletion of join models is direct, no destroy callbacks are triggered." i can not use callbacks for this.
In Task i need all project_ids to calculate a value for Project after Task is saved. How can i disable delete or change delete to destroy on has_many through association? What is best practise for this problem?
class Task has_many :project_tasks has_many :projects, :through => :project_tasks class ProjectTask belongs_to :project belongs_to :task class Project has_many :project_tasks has_many :tasks, :through => :project_tasks
Seems like i have to use associations callbacks
class Task has_many :project_tasks has_many :projects, :through => :project_tasks, :before_remove => :my_before_remove, :after_remove => :my_after_remove protected def my_before_remove(obj) ... end def my_after_remove(obj) ... end end
Problem with callbacks and has_many :through association, call a function that updates a score of the added venue. And here's the problem: I can't use after_add/after_remove callbacks in Reply model,� The :source option specifies the source association name for a has_many :through association. You only need to use this option if the name of the source association cannot be automatically inferred from the association name. 126.96.36.199 :source_type
This is what I did
in the model:
class Body < ActiveRecord::Base has_many :hands, dependent: destroy has_many :fingers, through: :hands, after_remove: :touch_self end
in my Lib folder:
module ActiveRecord class Base private def touch_self(obj) obj.touch && self.touch end end end
Active Record Associations — Ruby on Rails Guides, I was reminded of this fact recently while pairing with a … we eventually decided to go another route and use a different callback function. on a has_many or has_many, through: collection association, our callbacks can be� How a has_many :through association works in practice. When you’re beginning to work with Rails and ActiveRecord, it can be tough to wrap your head around the concept of has_many :through associations, and more importantly how they can be used in your Rails app.
Updating joins model associations, Rails add and remove records on the collection. To remove the records, Rails use the
delete method and this one will not call any destroy callback.
You can force Rails to call
delete when is removing records.
To do that, install the gem replace_with_destroy and pass the option
replace_with_destroy: true to the has_many association.
class Task has_many :project_tasks has_many :projects, :through => :project_tasks, replace_with_destroy: true ... end class ProjectTask belongs_to :project belongs_to :task # any destroy callback in this model will be executed #... end class Project ... end
Functions to Call Upon: ActiveRecord Association Callbacks, With a has_many association defined with a through option, the callbacks The output should include both a valid consultant_id and purpose_id , for example: Fix callbacks on has_many :through associations #35799. has_many :through. A has_many :through association is used to setup a many to many relationship with another model in your application. This association uses a join table to connect the models allowing each to both ‘has’ and ‘belong_to’ each model. In this case, our cop can have many perps to bust and our perps can belong to the many cops.
It seems like adding
dependent: :destroy to
has_many :through relation will destroy the join model (instead of delete). This is because CollectionAssociation#delete internally refers to
:dependent option to determine whether the passed records should be deleted or destroyed.
So in your case,
class Task has_many :project_tasks has_many :projects, :through => :project_tasks, :dependent => :destroy end
has_many-through-join-model record is incomplete in `after_add , This will also run validations and callbacks of associated object(s). If using with the :through option, the association on the join model must be a #belongs_to,� AKA "has many through" Overview. Many-to-many through associations behave in the same way as many-to-many associations, except that in a many-to-many through association, the join table is created automatically. In a many-to-many through assocation, you define a model containing two fields that correspond to the two models you will be joining
has_many (ActiveRecord::Associations::ClassMethods), So a straightway solution is setup all associations with dependent: :destroy in Client objects to be deleted directly from the database (so callbacks will not execute) To demonstrate, let me set up an example model: An important caveat with going through has_one or has_many associations on the join� I have a class with a has_many association. I have a after_add and an after_remove callback on the association, like this: # rails 4.2.0.alpha has_many :character_levels, after_add: :log_adding_event, after_remove: :log_removing_event de
Ruby on Rails: how to efficiently delete a mass of associated objects , If the :through option is true callbacks in the join models are triggered except So a Person class that makes a #has_many association will use “person_id” as� The has_many :through association is also useful for setting up “shortcuts” through nested has_many associations. For example, if a document has many sections, and a section has many paragraphs, you may sometimes want to get a simple collection of all paragraphs in the document.
Method: ActiveRecord::Associations::ClassMethods#has_many , The Rails 4 documentation says this regarding destroy callbacks on the join model for a has_many :through relationship: collection=objects� The has_many :through association is also useful for setting up "shortcuts" through nested has_many associations. For example, if a document has many sections, and a section has many paragraphs, you may sometimes want to get a simple collection of all paragraphs in the document.