From 03f8e549b55fae3b93dd8ffb38b02e0f81760535 Mon Sep 17 00:00:00 2001
From: Alex Reisner <alex@alexreisner.com>
Date: Wed, 30 Sep 2009 23:38:30 -0400
Subject: [PATCH] Generate options to ActiveRecord.find rather than raw SQL for
finding records near a given location.
---
README.rdoc | 19 +++---------
lib/geocoder.rb | 78 ++++++++++++++++++++++++++-----------------------
2 files changed, 46 insertions(+), 51 deletions(-)
diff --git a/README.rdoc b/README.rdoc
index 6539add0..873631ee 100644
--- a/README.rdoc
+++ b/README.rdoc
@@ -1,9 +1,6 @@
= Geocoder
-Geocoder is a simple plugin for Rails that provides object geocoding (via
-Google Maps) and some utilities for working with geocoded objects. The code can
-be used as a standalone method provider or included in a class to give objects
-geographic awareness.
+Geocoder is a simple plugin for Rails that provides object geocoding (via Google Maps) and some utilities for working with geocoded objects. The code can be used as a standalone method provider or included in a class to give objects geographic awareness.
== Setup
@@ -15,14 +12,11 @@ To add geocoding features to a class:
geocoded_by :location
-Be sure your class defines read/write attributes +latitude+ and +longitude+ as
-well as a method called +location+ (or whatever name you pass to +geocoded_by+)
-that returns a string suitable for passing to a Google Maps search, for example:
+Be sure your class defines read/write attributes +latitude+ and +longitude+ as well as a method called +location+ (or whatever name you pass to +geocoded_by+) that returns a string suitable for passing to a Google Maps search, for example:
714 Green St, Big Town, MO
-If your model has +address+, +city+, +state+, and +country+ attributes your
-+location+ method might look something like this:
+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(', ')
@@ -43,14 +37,9 @@ Find distance between object and a point:
Find objects within 20 miles of a point:
- Venue.near('Omaha, NE, US', 20) # Venue is a geocoded model
+ Venue.find_near('Omaha, NE, US', 20) # Venue is a geocoded model
Please see the code for more methods and detailed information about arguments.
-
-== To-do
-
-* +near+ method should also accept an array of coordinates as its first parameter
-
Copyright (c) 2009 Alex Reisner, released under the MIT license
diff --git a/lib/geocoder.rb b/lib/geocoder.rb
index 3c8a5d5e..745966cd 100644
--- a/lib/geocoder.rb
+++ b/lib/geocoder.rb
@@ -25,7 +25,7 @@ module Geocoder
# Returns array [lat,lon] if found, nil if not found or if network error.
#
def self.fetch_coordinates(query)
- doc = self.search(query)
+ return nil unless doc = self.search(query)
# Make sure search found a result.
e = doc.elements['kml/Response/Status/code']
@@ -46,25 +46,16 @@ module Geocoder
##
# Find all objects within a radius (in miles) of the given location
- # (address string).
+ # (address string). Location (the first argument) may be either a string
+ # to geocode or an array of coordinates (<tt>[lat,long]</tt>).
#
- def near(location, radius = 100, options = {})
- latitude, longitude = Geocoder.fetch_coordinates(location)
+ def find_near(location, radius = 20, options = {})
+ latitude, longitude = location.is_a?(Array) ?
+ location : Geocoder.fetch_coordinates(location)
return [] unless (latitude and longitude)
- query = nearby_mysql_query(latitude, longitude, radius.to_i, options)
- find_by_sql(query)
+ all(Geocoder.find_near_options(latitude, longitude, radius, options))
end
- ##
- # Generate a MySQL query to find all records within a radius (in miles)
- # of a point.
- #
- def nearby_mysql_query(latitude, longitude, radius = 20, options = {})
- table = options[:table_name] || self.to_s.tableize
- options.delete :table_name # don't pass to nearby_mysql_query
- Geocoder.nearby_mysql_query(table, latitude, longitude, radius, options)
- end
-
##
# Get the name of the method that returns the search string.
#
@@ -114,10 +105,11 @@ module Geocoder
units = { :mi => 3956, :km => 6371 }
# convert degrees to radians
- lat1 *= Math::PI / 180
- lon1 *= Math::PI / 180
- lat2 *= Math::PI / 180
- lon2 *= Math::PI / 180
+ lat1 = to_radians(lat1)
+ lon1 = to_radians(lon1)
+ lat2 = to_radians(lat2)
+ lon2 = to_radians(lon2)
+ # compute distances
dlat = (lat1 - lat2).abs
dlon = (lon1 - lon2).abs
@@ -128,7 +120,15 @@ module Geocoder
end
##
- # Find all records within a radius (in miles) of the given point.
+ # Convert degrees to radians.
+ #
+ def self.to_radians(degrees)
+ degrees * (Math::PI / 180)
+ end
+
+ ##
+ # Get options hash suitable for passing to ActiveRecord.find to get
+ # records within a radius (in miles) of the given point.
# Taken from excellent tutorial at:
# http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL
#
@@ -140,12 +140,13 @@ module Geocoder
# +limit+ :: number of records to return (for LIMIT SQL clause)
# +offset+ :: number of records to skip (for LIMIT SQL clause)
#
- def self.nearby_mysql_query(table, latitude, longitude, radius = 20, options = {})
+ def self.find_near_options(latitude, longitude, radius = 20, options = {})
- # Alternate column names.
+ # Set defaults/clean up arguments.
options[:latitude] ||= 'latitude'
options[:longitude] ||= 'longitude'
options[:order] ||= 'distance ASC'
+ radius = radius.to_i
# Constrain search to a (radius x radius) square.
factor = (Math::cos(latitude * Math::PI / 180.0) * 69.0).abs
@@ -153,25 +154,30 @@ module Geocoder
lon_hi = longitude + (radius / factor);
lat_lo = latitude - (radius / 69.0);
lat_hi = latitude + (radius / 69.0);
- where = "#{options[:latitude]} BETWEEN #{lat_lo} AND #{lat_hi} AND " +
- "#{options[:longitude]} BETWEEN #{lon_lo} AND #{lon_hi}"
# Build limit clause.
- limit = ""
+ limit = nil
if options[:limit] or options[:offset]
options[:offset] ||= 0
- limit = "LIMIT #{options[:offset]},#{options[:limit]}"
+ limit = "#{options[:offset]},#{options[:limit]}"
end
- # Generate query.
- "SELECT *, 3956 * 2 * ASIN(SQRT(" +
- "POWER(SIN((#{latitude} - #{options[:latitude]}) * " +
- "PI() / 180 / 2), 2) + COS(#{latitude} * PI()/180) * " +
- "COS(#{options[:latitude]} * PI() / 180) * " +
- "POWER(SIN((#{longitude} - #{options[:longitude]}) * " +
- "PI() / 180 / 2), 2) )) as distance " +
- "FROM #{table} WHERE #{where} HAVING distance <= #{radius} " +
- "ORDER BY #{options[:order]} #{limit}"
+ # Generate hash.
+ {
+ :select => "*, 3956 * 2 * ASIN(SQRT(" +
+ "POWER(SIN((#{latitude} - #{options[:latitude]}) * " +
+ "PI() / 180 / 2), 2) + COS(#{latitude} * PI()/180) * " +
+ "COS(#{options[:latitude]} * PI() / 180) * " +
+ "POWER(SIN((#{longitude} - #{options[:longitude]}) * " +
+ "PI() / 180 / 2), 2) )) as distance",
+ :conditions => [
+ "#{options[:latitude]} BETWEEN ? AND ? AND " +
+ "#{options[:longitude]} BETWEEN ? AND ?",
+ lat_lo, lat_hi, lon_lo, lon_hi],
+ :having => "distance <= #{radius}",
+ :order => options[:order],
+ :limit => limit
+ }
end
##
--
GitLab