Rails: Access parent model attributes in nested model validations

Question

I have Project model that has_many tasks . The Project model accepts_nested_attributes_for and validates_associated tasks .

In my @project form I'm submitting multiple tasks for each project in a single submit. I wish to run validations on my nested tasks based on the project type. As follows:

Task model:

  with_options if: :special_project? do |task|
    task.validate :is_possible
  end

  def special_project?
    project.cat == 'special'
  end

Unfortunately, Rails gives me a NilClass error

undefined method cat for nil:NilClass

Apparently the project_id attribute has not yet been set in the Task model (?).

How do I access a parent Project model attributes in my nested Task model during validation?

Answer 1

You might need to use inverse_of for this. By setting inverse_of to your models, Rails will use the same record objects in memory when accessing the associated records. Not entirely sure if this will work, but you could try.