delegated_association.ruby

class Household < ApplicationRecord
  has_many :members
  has_many :expenses
end

class Member < ApplicationRecord
  belongs_to :household
end

class Expense < ApplicationController
  belongs_to :household
  belongs_to :member
  
  # Better way to do this?
  def member
    if member_id && household.members.loaded?
      household.members.find { |m| m.id == member_id } || super
    else
      super
    end
  end
end

# Avoid double loading member records
Household.all.includes(:members, expenses: :member)

# Prefer:
Household.all.includes(:members, :expenses)

if member_id && !association(:member).loaded? && association(:household).loaded? && household.association(:members).loaded?

And with Preloaders

https://gist.github.com/p8/f6ae70e1ec7d33703e3e61ac0b79a843