Geocoder adds object geocoding and database-agnostic distance calculations to Ruby on Rails. It's as simple as calling fetch_coordinates! on your objects, and then using a named scope like Venue.near("Billings, MT").
Geocoder 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
A) Get a Google Maps API key (see code.google.com/apis/maps/signup.html) and store it in a constant:
# eg, in config/initializers/google_maps.rb GOOGLE_MAPS_API_KEY = "..."
B) Add latitude and longitude columns to your model:
script/generate migration AddLatitudeAndLongitudeToYourModel latitude:float longitude:float rake db:migrate
C) Tell geocoder where your model stores its address:
D) Optionally, auto-fetch coordinates every time your model is saved:
Note that you are not stuck with the latitude and longitude column names, or the address method. See “More On Configuration” below for details.
Assuming obj is an instance of a geocoded class, you can get its coordinates:
obj.fetch_coordinates # fetches and assigns coordinates obj.fetch_coordinates! # also saves lat, lon attributes
If you have a lot of objects you can use this Rake task to geocode them all:
rake geocode:all CLASS=YourModel
Once obj is geocoded you can do things like this:
obj.nearbys(30) # other objects within 30 miles obj.distance_to(40.714, -100.234) # distance to arbitrary point
To find objects by location, use 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
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") # find the geographic center (aka center of gravity) of objects or points Geocoder.geographic_center([ city1, city2, city3, [40.22,-73.99], city4 ])
More On Configuration
You are not stuck with using the latitude and longitude database column names for storing coordinates. For example, to use lat and lon:
geocoded_by :address, :latitude => :lat, :longitude => :lon
The string to use for geocoding can be anything you'd use to search Google Maps. For example, 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 you might do something like this:
geocoded_by :location def location [address, city, state, country].compact.join(', ') end
Please see the code for more methods and detailed information about arguments (eg, working with kilometers).
install.rb should do some setup when installed as a plugin
Copyright © 2009 Alex Reisner, released under the MIT license