has_many with date_part condition

model.rb

# using the awesome squeel gem

has_many :shares, dependent: :destroy
has_many :stories, through: :shares

has_many(
  :stories_this_month, -> do
    where do
      date_part('month', created_at).eq(Date.today.month) &
      date_part('year', created_at).eq(Date.today.year)
    end
  end,
  through: :shares,
  source: :story,
  class_name: 'Story'
)