streets_segments

class Segment < ActiveRecord::Base
  has_many :street_segments
  has_many :streets, :through => :street_segments, :source => :street

  after_save :ensure_primary

  def ensure_primary
    if self.streets.size > 0 && self.primary_street.nil? 
      # set the primary street attribute in association (in reality more criteria than just being 'first', but whatever)
      primary_street = self.street_segments.first
      primary_street.make_primary
    end
  end

  def primary_street
    self.street_segments.find_all { |st| st.prim == "1" }.first.street
  end
end

class StreetSegment < ActiveRecord::Base
  set_table_name "segments_streets"
  belongs_to :segment
  belongs_to :street

  def make_primary
    self.prim = 1
    self.save!
  end
end

class Street < ActiveRecord::Base
  has_many :addresses
  has_many :street_segments
  has_many :segments, :through => :street_segments, :source => :segment
end

class SegmentsController < ApplicationController
  def create
    @segment = Segment.new(params[:segment])

    @possible_streets = Street.find_by_sql "SELECT s.* FROM streets AS s ... WHERE ... GROUP BY s.id"
    @segment.streets = @possible_streets
    @segment.save!
  end
end