ruby on rails - Adding a record to a has_many_and_belongs_to association? -

i have 2 rails models of form:

class user < activerecord::base     has_many_and_belongs_to :tags end  class tag < activerecord::base     has_many_and_belongs_to :users end 

i have migration creates tags_users table.

how add record tags_users table? (tags , users unique)

i've trying doing

users.tag_ids << new_tag 

but not seem work. pointers welcome

there various ways achieve that, e.g:

u = user.first t = tag.create(name: 't') u.tag_ids << t.id  # or:  u = user.first t = tag.new(name: 't') u.tags << t 

you can't call collection_singular_ids (tag_ids in case) on collection. worth noting having habtm association, not have access join model explicitly (e.g taguser).