Allow separate address for reverse geocoding.

This allows the same model to be forward and reverse geocoded and still
provide a geocodable address though a non-attribute method. Also raise
an exception if sufficient configuration is not provided.

lib/geocoder.rb

@@ -12,7 +12,7 @@ ActiveRecord::Base.class_eval do
   #
   def self.geocoded_by(address_attr, options = {})
     _geocoder_init(
-      :address   => address_attr,
+      :user_address => address_attr,
       :latitude  => options[:latitude]  || :latitude,
       :longitude => options[:longitude] || :longitude
     )
@@ -23,7 +23,7 @@ ActiveRecord::Base.class_eval do
   #
   def self.reverse_geocoded_by(latitude_attr, longitude_attr, options = {})
     _geocoder_init(
-      :address   => options[:address] || :address,
+      :fetched_address => options[:address] || :address,
       :latitude  => latitude_attr,
       :longitude => longitude_attr
     )
@@ -44,3 +44,10 @@ ActiveRecord::Base.class_eval do
     included_modules.include? Geocoder::ActiveRecord
   end
 end
+
+
+class GeocoderError < StandardError
+end
+
+class GeocoderConfigurationError < GeocoderError
+end

lib/geocoder/active_record.rb

@@ -183,9 +183,13 @@ module Geocoder
     # coordinates as an array: <tt>[lat, lon]</tt>.
     #
     def fetch_coordinates(save = false)
-      coords = Geocoder::Lookup.coordinates(
-        send(self.class.geocoder_options[:address])
-      )
+      address_method = self.class.geocoder_options[:user_address]
+      unless address_method.is_a? Symbol
+        raise GeocoderConfigurationError,
+          "You are attempting to fetch coordinates but have not specified " +
+          "a method which provides an address for the object."
+      end
+      coords = Geocoder::Lookup.coordinates(send(address_method))
       unless coords.blank?
         method = (save ? "update" : "write") + "_attribute"
         send method, self.class.geocoder_options[:latitude],  coords[0]
@@ -206,13 +210,17 @@ module Geocoder
     # address as a string.
     #
     def fetch_address(save = false)
-      address = Geocoder::Lookup.address(
-        send(self.class.geocoder_options[:latitude]),
-        send(self.class.geocoder_options[:longitude])
-      )
+      lat_attr = self.class.geocoder_options[:latitude]
+      lon_attr = self.class.geocoder_options[:longitude]
+      unless lat_attr.is_a?(Symbol) and lon_attr.is_a?(Symbol)
+        raise GeocoderConfigurationError,
+          "You are attempting to fetch an address but have not specified " +
+          "attributes which provide coordinates for the object."
+      end
+      address = Geocoder::Lookup.address(send(lat_attr), send(lon_attr))
       unless address.blank?
         method = (save ? "update" : "write") + "_attribute"
-        send method, self.class.geocoder_options[:address], address
+        send method, self.class.geocoder_options[:fetched_address], address
       end
       address
     end

test/geocoder_test.rb

@@ -20,4 +20,11 @@ class GeocoderTest < Test::Unit::TestCase
     assert_equal [0.0, 1.0],
       Geocoder::Calculations.geographic_center([[0,0], [0,1], [0,2]])
   end
+
+  def test_exception_raised_for_unconfigured_geocoding
+    l = Landmark.new("Mount Rushmore", 43.88, -103.46)
+    assert_raises GeocoderConfigurationError do
+      l.fetch_coordinates
+    end
+  end
 end

test/test_helper.rb

@@ -65,6 +65,27 @@ class Venue < ActiveRecord::Base
   end
 end
 
+##
+# Reverse geocoded model.
+#
+class Landmark < ActiveRecord::Base
+  reverse_geocoded_by :latitude, :longitude
+
+  def initialize(name, latitude, longitude)
+    super()
+    write_attribute :name, name
+    write_attribute :latitude, latitude
+    write_attribute :longitude, longitude
+  end
+
+  ##
+  # If method not found, assume it's an ActiveRecord attribute reader.
+  #
+  def method_missing(name, *args, &block)
+    @attributes[name]
+  end
+end
+
 class Test::Unit::TestCase
   def venue_params(abbrev)
     {