Question

Here is my scenario:

A model called Course has many CourseCodes. A CourseCode belongs to a Course.
A CourseCode can’t be created without Course and a Course can’t be created without at least one CourseCode.

class Course < ActiveRecord::Base
  has_many :course_codes
  validate :existence_of_code
private
  def existence_of_code
    unless course_codes.any?
      errors[:course_codes] << "missing course code"
    end
  end
end

class CourseCode < ActiveRecord::Base
  belongs_to :course
  validates_presence_of :course
end

The whole scenario feels a bit like catch 22.
Is there a way to create both on the same time?
I’m using Rails 3.2

Answer 1

Solved the problem by using accepts_nested_attributes_for.

Nested attributes allow you to save attributes on associated records through the parent. By default nested.

class Course < ActiveRecord::Base
  has_many :course_codes, inverse_of: :course
  validate :existence_of_code

  accepts_nested_attributes_for :course_codes

private
  def existence_of_code
    unless course_codes.any?
      errors[:course_codes] << "missing course code"
    end
  end
end

class CourseCode < ActiveRecord::Base
  belongs_to :course, inverse_of: :course_codes
  validates_presence_of :course
end

Used like this.

Course.create!({
  course_codes_attributes: [{ code: "TDA123" }],
  # ...
})