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SpatialAssociations
===================

SpatialAssociations provides helper methods for ActiveRecord::Base that enable spatially constrained associations.

A Spatial Association is one where the coupling between models is determined by the result of a geometric function, rather than a relational key-based linking.

This plugin assumes that you are using PostGIS, and that your geometric columns are all named 'geometry'.


Helpers Available
=================

is_enclosed_by :model
	i.e. a city is_enclosed_by a state.
	
encloses :models
	i.e. a state encloses cities.


Example
=======

Say I have two spatial enabled models, City and State.

Add the helpers to the appropriate models:

	class City < ActiveRecord::Base
		is_enclosed_by :state
	end

	class State < ActiveRecord::Base
		encloses :cities
	end

I can now use these associations as follows:

@someCitysState = @someCityObject.state # => Returns a state object that spatially encloses the receiving city.

@someStatesCities = @someStateObject.cities # => Returns an array of City objects which are spatially enclosed by the receiving state.

Copyright (c) 2008 Bradley Spaulding, released under the MIT license