Geokit and rails 3

Question

Hi,

I am using the geokit gem and plugin with rails 3. It seems there is a known issue with them, which can be seen here http://github.com/andre/geokit-rails/issues#issue/15

Now, I tried to follow the solution provided at the bottom. I pasted that function definition, at the end of the file, just above acts_as_mapable, and just after the first time it was called, but nothing happened each time.

Any idea what else can be done?

Thanks

Answer 1

Hey Amit, Not sure if you sorted this out yet but I'll tell you what I did just in case.

I forked andre's geokit-rails source and then cloned it locally and added the code from this gist at line 34 of lib/geokit-rails/acts-as-mappable.rb, just after the line that reads module ClassMethods # :nodoc:.

Then I commited those changes back to my forked repo on github and used my fork to install the source as a plugin to my rails 3 app. That seemed to work straight away, but make sure you have the acts_as_mappable line added to whatever model you are wanting to do distance calculations on and make sure you have two float columns on that db named :lat and :lng.

Answer 2

I ran into similar problems upgrading my app to rails 3. I'm still using Geokit for geocoding but Active Record scopes for distance based database queries. It's pretty convenient, and you still get all of the Active Record 3 goodness. Here's an example from my User model:

scope :near, lambda{ |*args|
                  origin = *args.first[:origin]
                  if (origin).is_a?(Array)
                    origin_lat, origin_lng = origin
                  else
                    origin_lat, origin_lng = origin.lat, origin.lng
                  end
                  origin_lat, origin_lng = deg2rad(origin_lat), deg2rad(origin_lng)
                  within = *args.first[:within]
                  { 
                    :conditions => %(
                      (ACOS(COS(#{origin_lat})*COS(#{origin_lng})*COS(RADIANS(users.lat))*COS(RADIANS(users.lng))+
                      COS(#{origin_lat})*SIN(#{origin_lng})*COS(RADIANS(users.lat))*SIN(RADIANS(users.lng))+
                      SIN(#{origin_lat})*SIN(RADIANS(users.lat)))*3963) <= #{within}
                    ),
                    :select => %( users.*,
                      (ACOS(COS(#{origin_lat})*COS(#{origin_lng})*COS(RADIANS(users.lat))*COS(RADIANS(users.lng))+
                      COS(#{origin_lat})*SIN(#{origin_lng})*COS(RADIANS(users.lat))*SIN(RADIANS(users.lng))+
                      SIN(#{origin_lat})*SIN(RADIANS(users.lat)))*3963) AS distance
                    )
                  }
                }

Here's a blog post with a little more detail on the subject: http://stcorbett.com/code/distance-queries-with-rails-3-without-geokit/