Question

We know that the distance field gets dropped when using the Geokit gem in Rails with acts_as_mappable :through model class. I wonder if there’s a way to work around this to get the distance field back. I tried to follow the monkey-patching example over here:
http://www.sobyteme.com/news/2010/05/13/computers/2010/06/25/geokit-acts_as_mappable-through-with-distance-attribute/
but it didn’t work for me.

Answer 1

Well, Steve’s suggestion over on his site was accurate, I was missing calling sort_by_distance_from after doing the find. So credit goes to him for this answer.

I’m on Rails v3.0.7. Here’s my code:

class Office < ActiveRecord::Base
    has_many :users
    acts_as_mappable :default_units => :miles, 
                     :default_formula => :sphere, 
                     :lat_column_name => :latitude,
                     :lng_column_name => :longitude
end

class User < ActiveRecord::Base
    belongs_to  :office
    acts_as_mappable :through => :office
end

users_controller.rb:

# Monkey patching to include the 'distance' attribute
module Geokit
  module Mappable
    def to_lat_lng
      return self if instance_of?(Geokit::LatLng) || instance_of?(Geokit::GeoLoc)
      return LatLng.new(self.office.send(self.office.class.lat_column_name),
        self.office.send(self.office.class.lng_column_name)) if self.class.respond_to?(:acts_as_mappable)
      nil
    end
  end 
end

class UsersController < ApplicationController

  def location
    @lat = params[:lat].to_f
    @long = params[:long].to_f
    @origin = [@lat, @long]
    @users = User.find(:all, 
         :origin => @origin,
         :conditions => "distance < 3")

    # We have to add this to get the 'distance' field
    @users.sort_by_distance_from(@origin)

    respond_to do |format|
      format.html
      format.xml  { render :xml => @users.to_xml(:methods => :distance)}
      format.json  { render :json => @users.to_json(:methods => :distance)}
    end
  end 
...
end