GeoKit Excerpt.rb

      # Class singleton methods to mix into ActiveRecord.
      module SingletonMethods # :nodoc:
        # Extends the existing find method in potentially two ways:
        # - If a mappable instance exists in the options, adds a distance column.
        # - If a mappable instance exists in the options and the distance column exists in the
        #   conditions, substitutes the distance sql for the distance column -- this saves
        #   having to write the gory SQL.
        def find(*args)
          options = extract_options_from_args!(args)
          origin = extract_origin_from_options(options)
          units = extract_units_from_options(options)
          formula = extract_formula_from_options(options)
          add_distance_to_select(options, origin, units, formula) if origin
          apply_find_scope(args, options)
          apply_distance_scope(options)
          substitute_distance_in_conditions(options, origin, units, formula) if origin && options.has_key?(:conditions)
          args.push(options)
          super(*args)
        end     
        
        # Finds within a distance radius.
        def find_within(distance, options={})
          options[:within] = distance
          find(:all, options)
        end
        alias find_inside find_within
        
        # Finds beyond a distance radius.
        def find_beyond(distance, options={})
          options[:beyond] = distance
          find(:all, options)
        end
        alias find_outside find_beyond
        
        # Finds according to a range.  Accepts inclusive or exclusive ranges.
        def find_by_range(range, options={})
          options[:range] = range
          find(:all, options)
        end
        
        # Finds the closest to the origin.
        def find_closest(options={})
          find(:nearest, options)
        end
        alias find_nearest find_closest
        
        # Finds the farthest from the origin.
        def find_farthest(options={})
          find(:farthest, options)
        end
        
        # Returns the distance calculation to be used as a display column or a condition.  This
        # is provide for anyone wanting access to the raw SQL.
        def distance_sql(origin, units=default_units, formula=default_formula)
          case formula
          when :sphere
            sql = sphere_distance_sql(origin, units)
          when :flat
            sql = flat_distance_sql(origin, units)
          end
          sql
        end