geospatial_object.rb

module GeospatialObject
  METERS_PER_MILE = 1609.34
  
  module Callbacks
    def set_geographic_point
      ActiveRecord::Base.connection.execute(<<-TEXT
        UPDATE addresses
        SET geographic_point = ST_GeographyFromText('POINT(' || longitude || ' ' || latitude || ')')
        WHERE id = #{self.id}
      TEXT
      )
    end
  end
  
  def self.extended(base)
    base.send(:include, Callbacks)
    base.after_save :set_geographic_point
    base.set_rgeo_factory_for_column(
      :geographic_point,
      RGeo::Geographic.spherical_factory(srid: 4326)
    )
  end
  
  def by_location(coordinates, distance_in_miles)
    distance_in_meters = distance_in_miles * METERS_PER_MILE

    if coordinates.blank?
      scoped
    else
      where(
        "ST_DWithin(geographic_point, st_setsrid(st_makepoint(?, ?), 4326), ?)",
        coordinates[:longitude],
        coordinates[:latitude],
        distance_in_meters
      )
    end
  end

  def order_by_distance(coordinates)
    if coordinates.blank?
      scoped
    else
      order(distance_from_coordinates(coordinates))
    end
  end

 def distance_from_coordinates(coordinates)
    search_point = RGeo::Geographic.spherical_factory.point(
      coordinates[:longitude],
      coordinates[:latitude]
    )

    "ST_Distance(geographic_point, ST_GeographyFromText('#{search_point}'))/#{METERS_PER_MILE}"
 end

   module_function :distance_from_coordinates
 end