Salaries

pay_stub.rb

class PayStub
  belongs_to :salary
  
  attr_accessor :start_date, :end_date
end

salary.rb

class Salary
  belongs_to :user
  has_many :pay_stubs

  def historic_pay_stubs(to_date, end_date)
    pay_stubs.select do |stub|
      stub.start_date >= to_date && stub.end_date <= end_date
    end
  end
end

user.rb

class User
  has_many :salaries
  has_many :pay_stubs, through: :salaries
  
  def historic_pay_stubs(to_date, end_date)
    pay_stubs.select do |stub|
      stub.start_date >= to_date && stub.end_date <= end_date
    end
  end
end