Geocoding addresses with geocoder gem and PostGIS database with RGeo

Question

I am trying to use the geocoder gem for looking up addresses and coordinates. I want it to work together with my PostGIS spatial database and the RGeo gem, which uses POINT features instead of saving latitude and longitude values separately. So I have tried to work into my model to save the results from the geocoder lookup into an RGeo POINT feature:

class Location < ActiveRecord::Base
  attr_accessible :latlon, :name, :address
  set_rgeo_factory_for_column(:latlon, RGeo::Geographic.spherical_factory(:srid => 4326))

  geocoded_by :name_and_address do |obj, results|
    if geo = results.first
      obj.latlon = Location.rgeo_factory_for_column(:latlon).point(geo.longitude, geo.latitude)
    end
  end

  after_initialize :init
  after_validation :geocode


  def init
    self.latlon ||= Location.rgeo_factory_for_column(:latlon).point(0, 0)
  end

  def latitude
    self.latlon.lat
  end

  def latitude=(value)
    lon = self.latlon.lon
    self.latlon = Location.rgeo_factory_for_column(:latlon).point(lon, value)
  end

  def longitude
    self.latlon.lon
  end

  def longitude=(value)
    lat = self.latlon.lat
    self.latlon = Location.rgeo_factory_for_column(:latlon).point(value, lat)
  end

  def name_and_address
    "#{self.name}, #{self.address}"
  end

end

In the Rails console I can now do:

test = Location.new(name: "Eiffel Tower") // => #<Location id: nil, name: "Eiffel Tower", latlon: #<RGeo::Geographic::SphericalPointImpl:0x81579974 "POINT (0.0 0.0)">, created_at: nil, updated_at: nil, address: nil>
test.geocode    //  => #<RGeo::Geographic::SphericalPointImpl:0x81581ac0 "POINT (2.294254 48.858278)">

Wonderful! However, when I want to save my test Location, which triggers the :after_validation call for :geocode I get an error:

NoMethodError: undefined method `lon' for nil:NilClass
    from /Users/sg/rails-projects/geo_rails_test/app/models/location.rb:24:in `latitude='
    from /Users/sg/rails-projects/geo_rails_test/app/models/location.rb:7:in `block in <class:Location>'
    from /Users/sg/.rvm/gems/ruby-1.9.3-p194/gems/geocoder-1.1.2/lib/geocoder/stores/base.rb:108:in `call'
    from /Users/sg/.rvm/gems/ruby-1.9.3-p194/gems/geocoder-1.1.2/lib/geocoder/stores/base.rb:108:in `do_lookup'
    from /Users/sg/.rvm/gems/ruby-1.9.3-p194/gems/geocoder-1.1.2/lib/geocoder/stores/active_record.rb:278:in `geocode'
    from /Users/sg/.rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `_run__1498365873506454431__validation__51840359655181017__callbacks'
    [...]

It seems that the geocode callback deletes the RGeo object so that its built in methods as well as my getter and setter methods are no longer available. Why? Any ideas?

donsteffenski donsteffenski · Accepted Answer · 2012-11-17T19:28:08

It was a bloody typo...

It works. I leave it up, maybe someone else has the same issue or a better solution...

I have also added the reverse_geocode case.

Now look what it can do:

1.9.3p194 :310 > loc = Location.new(name: "Vatikan")
 => #<Location id: nil, name: "Vatikan", latlon: #<RGeo::Geographic::SphericalPointImpl:0x8148add8 "POINT (0.0 0.0)">, created_at: nil, updated_at: nil, address: nil> 
1.9.3p194 :311 > loc.save
   (0.2ms)  BEGIN
  SQL (0.6ms)  INSERT INTO "locations" ("address", "created_at", "latlon", "name", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["address", "Via Pio X, 00120, Vatican City"], ["created_at", Sat, 17 Nov 2012 19:26:59 UTC +00:00], ["latlon", #<RGeo::Geographic::SphericalPointImpl:0x81570554 "POINT (12.453389 41.902916)">], ["name", "Vatikan"], ["updated_at", Sat, 17 Nov 2012 19:26:59 UTC +00:00]]
   (0.9ms)  COMMIT
 => true

I love this! :-)

Geocoding addresses with geocoder gem and PostGIS database with RGeo

1 Answers