Geokit Rails距离并找到（：全部）

Question

I have 2 questions regarding the gem 'geokit-rails'

This is my sample code

class Outlet < ActiveRecord::Base
  acts_as_mappable :lat_column_name => :address_latitude,
                   :lng_column_name => :address_longitude,
                   :default_units => :kms
end            

1. I cant use the find(:all)

   sample Outlet.find(:all, :origin =>[32.951613,-96.958444], :within=>10) it returns ActiveRecord::RecordNotFound: Couldn't find all Outlets with 'id': (all, {:origin=>[32.951613, -96.958444], :within=>10})

   I have also tested on this query Outlet.find(:all) it returns ActiveRecord::RecordNotFound: Couldn't find Outlet with 'id'=all

2. Distance. I dont really understand how does this work. Should we add distance column into the the outlet model ? If yes, whats the column type? And is that possible to return the record with the distance value based on the given lat lng ? Outlet.by_distance(:origin =>[32.951613, -96.958444]) it will return the records with the distance to that point. (2kms, 3kms, 4km, ...)

Answer 1

1. find is an ActiveRecord method. It has nothing to do with Geokit . It takes model id such as 1 for the first Outlet you created or 2 for the second Outlet. You used Outlet.find(:all) so, ActiveRecord complained that it could not find any Outlet with id all .

   I think what you actually wanted to do is

    Outlet.within(10, :origin => [32.951613,-96.958444]) 

   Note that you can also pass an object for origin, for example,

    @the_latest_outlet = Outlet.last @outlets_nearby_the_latest_outlet = Outlet.within(10, origin: @the_latest_outlet) 

2. No, you don't have to add a column. The field distance is added to ActiveRecord instances automatically. I still haven't found any use of the parameter :distance_field_name . My best guess is that if your model has a field named distance , you should use distance_field_name parameter to avoid the conflict.

   2.1. If you want to measure distance between 2 points, you need distance_to as this example:

    a = Outlet.find(1) b = Outlet.find(2) distance_from_a_to_b = a.distance_to(b) 

   2.2. by_distance is to get all your instances sorted by distance.

    a_place_to_compare = [lat, lng] all_outlets_sorted_by_distance_from_the_place = Outlet.by_distance(a_place_to_compare)