- has_one :from_node, :class => 'Node', :foreign_key => 'node_a'
- has_one :to_node, :class => 'Node', :foreign_key => 'node_b'
+ has_one :from_node, :class_name => 'Node', :foreign_key => 'id'
+ has_one :to_node, :class_name => 'Node', :foreign_key => 'id'