child_association.rb

class Child < ActiveRecord::Base
  belongs_to :parent
end

# rails console
>> Child.reflect_on_all_associations
Child.reflect_on_all_associations
=> [#<ActiveRecord::Reflection::AssociationReflection:0xb4828958 
   @options={}, 
   @collection=false,
   @name=:parent,
   @active_record=Child(id: integer, name: string, parent_id: integer),
   @macro=:belongs_to>]