Module: ActiveRecordSpatial::Associations

Extended by:: ActiveSupport::Concern

Included in:: ActiveRecord::Base

Defined in:: lib/activerecord-spatial/associations/base.rb,
lib/activerecord-spatial/associations.rb

Overview

ActiveRecord Spatial associations allow for has_many-style associations using spatial relationships.

Example

class Neighbourhood < ActiveRecord::Base
  has_many_spatially :cities,
    relationship: :contains
end

class City < ActiveRecord::Base
  has_many_spatially :neighbourhoods, -> {
    where('canonical = true')
  }, relationship: :within
end

Neighbourhood.first.cities
#=> All cities that the neighbourhood is within

City.first.neighbourhoods
#=> All neighbourhoods contained by the city

City.includes(:neighbourhoods).first.neighbourhoods
#=> Eager loading works too

Spatial associations can be set up using any of the relationships found in ActiveRecordSpatial::SpatialScopes::RELATIONSHIPS.

Options

Many of the options available with standard has_many associations will work with the exceptions of :through, :source, :source_type, :dependent, :finder_sql, :counter_sql, and :inverse_of.

Polymorphic relationships can be used via the :as option as in standard :has_many relationships. Note that the default field for the geometry in these cases is “#association_name_geom” and can be overridden using the :foreign_geom option.

:relationship - sets the spatial relationship for the association. Valid options can be found in ActiveRecordSpatial::SpatialScopes::RELATIONSHIPS. The default value is :intersects.
:geom - sets the geometry field for the association in the calling model. The default value is :the_geom as is often seen in PostGIS documentation.
:foreign_geom - sets the geometry field for the association’s foreign table. The default here is again :the_geom.
:scope_options - these are options passed directly to the SpatialScopes module and as such the options are the same as are available there. The default value here is { invert: true }, as we want our spatial relationships to say “Foo spatially contains many Bars” and therefore the relationship in SQL becomes ST_contains("foos"."the_geom", "bars"."the_geom").

Note that you can modify the default geometry column name for all of ActiveRecordSpatial by setting it via ActiveRecordSpatia.default_column_name.

Caveats

You should consider spatial associations to be essentially readonly. Since we’re not dealing with unique IDs here but rather 2D and 3D geometries, the relationships between rows don’t really map well to the traditional foreign key-style ActiveRecord associations.

Defined Under Namespace

Modules: ClassMethods

Constant Summary collapse

DEFAULT_OPTIONS =

{
  relationship: :intersects,
  geom: ActiveRecordSpatial.default_column_name,
  foreign_geom: ActiveRecordSpatial.default_column_name,
  scope_options: {
    invert: true
  }
}.freeze