Please explain rails has_many through association -

i'm trying understand rails associations

i've following tables , i've define relations, can 1 please me understand. tables products, productdistributors, , distributors. every product has distributor, distributor carries multiple products

i defined these

class product < activerecord::base    has_one :product_distributor    has_one  :distributor, through: :product_distributor end class productdistributor < activerecord::base    belongs_to :products    belongs_to :distributors    end class distributor < activerecord::base    has_many :product_distributors    has_many :products, through: :product_distributors end 

is correct? if not, how can correct it?

i feel problem lies in distributors class name because it's plural. when has_many :distributors, rails default link distributor class, in case class name distributors.

adding class_name option relationship declarations should work:

class product < activerecord::base    has_one :product_distributor    has_one  :distributor, through: :product_distributor, class_name: 'distributors' end class productdistributor < activerecord::base    belongs_to :product    belongs_to :distributor, class_name: 'distributors'  end class distributors < activerecord::base    has_many :product_distributors    has_many :products, through: :product_distributors end 

also note belongs_to should singular not plural. please go through association guide details: http://guides.rubyonrails.org/association_basics.html.