ruby on rails - accepts_nested_attributes_for child association validation failing

Question

I'm using accepts_nested_attributes_for in one of my Rails models, and I want to save the children after creating the parent.

The form works perfectly, but the validation is failing. For simplicity's sake imagine the following:

class Project < ActiveRecord::Base
  has_many :tasks
  accepts_nested_attributes_for :tasks
end

class Task < ActiveRecord::Base
  belongs_to :project

  validates_presence_of :project_id
  validates_associated :project
end

And I am running:

Project.create!(
  :name => 'Something',
  :task_attributes => [ { :name => '123' }, { :name => '456' } ]
)

Upon saving the project model, the validation is failing on the tasks because they don't have a project_id (since the project hasn't been saved).

It seems like Rails is following the pattern below:

• Validate Project
• Validate Tasks
• Save Project
• Save Tasks

The pattern should be:

• Validate Project
• On Pass: Save Project and continue...
• Validate Tasks
  • On Pass: Save Tasks
  • On Fail: Delete Project (rollback maybe?)

So my question boils down to: How can I get Rails to run the project_id= (or project=) method and validation on the children (tasks) AFTER the parent (project) has been saved, but NOT save the parent (project) model if any child (task) is invalid?

Any ideas?

Answer 1

Use :inverse_of and validates_presence_of :parent. This should fix your validation problem.

   class Dungeon < ActiveRecord::Base
     has_many :traps, :inverse_of => :dungeon
   end

   class Trap < ActiveRecord::Base
     belongs_to :dungeon, :inverse_of => :traps
     validates_presence_of :dungeon
   end

http://apidock.com/rails/ActiveModel/Validations/HelperMethods/validates_presence_of

https://github.com/rails/rails/blob/73f2d37505025a446bb5314a090f412d0fceb8ca/activerecord/test/cases/nested_attributes_test.rb