Geocoder adds object geocoding and database-agnostic distance calculations to Ruby on Rails. It does not rely on proprietary database functions so finding geocoded objects in a given area is easily done using out-of-the-box MySQL or even SQLite.
Install either as a plugin:
script/plugin install git://github.com/alexreisner/geocoder.git
or as a gem:
# add to config/environment.rb: config.gem "rails-geocoder", :lib => "geocoder", :source => "http://gemcutter.org/" # at command prompt: sudo rake gems:install
First, you must get a Google Maps API key (to get one go to code.google.com/apis/maps/signup.html) and store it in a constant:
GOOGLE_MAPS_API_KEY = "..."
To add geocoding features to a class:
Be sure your class defines attributes for storing latitude and longitude (use float or double database columns) and a location (human-readable address to be geocoded). These attribute names are all configurable; for example, to use address, lat, and lon respectively:
geocoded_by :address, :latitude => :lat, :longitude => :lon
A geocodable string is anything you'd use to search Google Maps. Any of the following are acceptable:
714 Green St, Big Town, MO Eiffel Tower, Paris, FR Paris, TX, US
If your model has address, city, state, and country attributes your location method might look something like this:
def location [address, city, state, country].compact.join(', ') end
Assuming Venue is a geocoded model, it has the following named scopes:
Venue.near('Omaha, NE, US', 20) # venues within 20 miles of Omaha Venue.near([40.71, 100.23], 20) # venues within 20 miles of a point Venue.geocoded # venues with coordinates Venue.not_geocoded # venues without coordinates
Assuming obj has a valid string for its location:
obj.fetch_coordinates # returns coordinates [lat, lon] obj.fetch_coordinates! # also writes coordinates to object
Assuming obj is geocoded (has latitude and longitude):
obj.nearbys(30) # other objects within 30 miles obj.distance_to(40.714, -100.234) # distance to arbitrary point
Some utility methods are also available:
# distance (in miles) between Eiffel Tower and Empire State Building Geocoder.distance_between( 48.858205,2.294359, 40.748433,-73.985655 ) # look up coordinates of some location (like searching Google Maps) Geocoder.fetch_coordinates("25 Main St, Cooperstown, NY")
Please see the code for more methods and detailed information about arguments (eg, working with kilometers).
Copyright © 2009 Alex Reisner, released under the MIT license