ruby - Rails has_and_belongs_to_many collection methods not showing up on object -

i have problem has_and_belongs_to_many in rails 4 app. setup follows:

• a user can have several roles
• a role can have several permissions

since many users can share same roles, , many roles can share same permissions, , don't need special connection models between them, using has_and_belongs_to_many both these relationships.

here models (stripped of validations):

class user < activerecord::base   has_and_belongs_to_many :roles end  class role < activerecord::base   has_and_belongs_to_many :permissions   has_and_belongs_to_many :users end  class permission < activerecord::base   has_and_belongs_to_many :roles end 

the join tables named per convention:

create_table "permissions_roles" |t|   t.integer "role_id"   t.integer "permission_id" end  create_table "roles_users" |t|   t.integer "role_id"   t.integer "user_id" end 

roles <-> permissions works great, users <-> roles seems work 1 way. can attach users roles, not roles users – collection methods not exist on user objects. rails console:

> r = role.first # fetch role > r.users        # empty list of users -- far > u = user.first # fetch user > u.roles        # nomethoderror: undefined method `roles' #<user:0x007fe67562f580> 

any idea going on here?

update:

when run user.has_and_belongs_to_many :roles console, association correctly set , can run user.first.roles without issue. seems association reason isn't set when application bootstrapped.

maybe should consider using has_many, :through

here example

from rubyonrails.org:

class assembly < activerecord::base   has_many :manifests   has_many :parts, through: :manifests end  class manifest < activerecord::base   belongs_to :assembly   belongs_to :part end  class part < activerecord::base   has_many :manifests   has_many :assemblies, through: :manifests end 

more ressources on:

1. the-has-many-through-association
2. choosing-between-has-many-through-and-has-and-belongs-to-many