Add reverse geocoding to models.

README.rdoc

@@ -101,6 +101,18 @@ If your model has +address+, +city+, +state+, and +country+ attributes you might
 Please see the code for more methods and detailed information about arguments (eg, working with kilometers).
 
 
+== Reverse Geocoding
+
+If you need reverse geocoding (lat/long coordinates to address), do something like the following in your model:
+
+  reverse_geocoded_by :latitude, :longitude
+  after_validation :fetch_address
+
+and make sure it has +latitude+ and +longitude+ attributes, as well as an +address+ attribute. As with regular geocoding, you can specify alternate names for all of these attributes, for example:
+
+  reverse_geocoded_by :lat, :lon, :address => :location
+
+
 == SQLite
 
 SQLite's lack of trigonometric functions requires an alternate implementation of the +near+ method (scope). When using SQLite, Geocoder will automatically use a less accurate algorithm for finding objects near a given point. Results of this algorithm should not be trusted too much as it will return objects that are outside the given radius.
@@ -136,7 +148,6 @@ If anyone has a more elegant solution to this problem I am very interested in se
 * use completely separate "drivers" for different AR adapters?
   * seems reasonable since we're using very DB-specific features
   * also need to make sure 'mysql2' is supported
-* add reverse geocoding
 * make 'near' scope work with AR associations
   * http://stackoverflow.com/questions/3266358/geocoder-rails-plugin-near-search-problem-with-activerecord
 * prepend table names to column names in SQL distance expression (required

lib/geocoder.rb

@@ -11,12 +11,36 @@ ActiveRecord::Base.class_eval do
   # Set attribute names and include the Geocoder module.
   #
   def self.geocoded_by(address_attr, options = {})
-    class_inheritable_reader :geocoder_options
-    write_inheritable_attribute :geocoder_options, {
-      :address_attr => address_attr,
-      :latitude     => options[:latitude]  || :latitude,
-      :longitude    => options[:longitude] || :longitude
-    }
-    include Geocoder::ActiveRecord
+    _geocoder_init({
+      :address   => address_attr,
+      :latitude  => options[:latitude]  || :latitude,
+      :longitude => options[:longitude] || :longitude
+    })
+  end
+
+  ##
+  # Set attribute names and include the Geocoder module.
+  #
+  def self.reverse_geocoded_by(latitude_attr, longitude_attr, options = {})
+    _geocoder_init({
+      :address   => options[:address] || :address,
+      :latitude  => latitude_attr,
+      :longitude => longitude_attr
+    })
+  end
+
+  def self._geocoder_init(options)
+    unless _geocoder_initialized?
+      class_inheritable_reader :geocoder_options
+      class_inheritable_hash_writer :geocoder_options
+    end
+    self.geocoder_options = options
+    unless _geocoder_initialized?
+      include Geocoder::ActiveRecord
+    end
+  end
+
+  def self._geocoder_initialized?
+    included_modules.include? Geocoder::ActiveRecord
   end
 end

lib/geocoder/active_record.rb

@@ -184,7 +184,7 @@ module Geocoder
     #
     def fetch_coordinates(save = false)
       coords = Geocoder::Lookup.coordinates(
-        send(self.class.geocoder_options[:address_attr])
+        send(self.class.geocoder_options[:address])
       )
       unless coords.blank?
         method = (save ? "update" : "write") + "_attribute"
@@ -200,5 +200,28 @@ module Geocoder
     def fetch_coordinates!
       fetch_coordinates(true)
     end
+
+    ##
+    # Fetch address and assign +address+ attribute. Also returns
+    # 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])
+      )
+      unless address.blank?
+        method = (save ? "update" : "write") + "_attribute"
+        send method, self.class.geocoder_options[:address], address
+      end
+      address
+    end
+
+    ##
+    # Fetch address and update (save) +address+ data.
+    #
+    def fetch_address!
+      fetch_address(true)
+    end
   end
 end