double belongs_to with validation on rails-CodePudding

I have the following models

   class School
      has_many :classrooms
      has_many :communications
    end

   class Classroom
      belongs_to :school
    end

    class Communication
      belongs_to :school
    end

At the moment I can have a school_id in communication, however due to business logic I realized that I might have to index the communication also with a classroom, making the models to be like this:

    class School
      has_many :classrooms
      has_many :communications
    end

   class Classroom
      belongs_to :school
      has_many :communications
    end

    class Communication
      belongs_to :school
      belongs_to :classroom, optional: true
    end

What I want is that a communication should always belong to a school, but if it belongs to a classroom i want to make sure that the classroom also belongs to the same school

How can I write a validation for this case?

CodePudding user response：

For this case I ended up creating a custom validator:

class ClassroomValidator < ActiveModel::Validator
  def validate(record)
    if record.classroom.school.id != record.school.id
      record.errors.add :classroom, message: "Invalid relation between classroom and school"
    end
  end
end
class Communication < ApplicationRecord
  belongs_to :school
  belongs_to :classroom, optional: true
  
  validates_with ClassroomValidator, if: -> { self.classroom != nil }
 
end