ruby on rails - Restricting a portion of code through an association -

i have built ruby on rails app lets users track workouts. user has_many workouts. in addition, user can create box (gym) if gym owner. purpose filter activity of users such can see information related gym. users can specify if member of box through membership model. membership table collects @box.id , current_user.id in membership.box_id , user.id columns respectively.

the user associates through following form in /views/boxes/show.html.erb view:

<% remote_form_for membership.new |f| %>    <%= f.hidden_field :box_id, :value => @box.id %>   <%= f.hidden_field :user_id, :value => current_user.id %>   <%= submit_tag "i member of box" , :class => '' %> <% end %> 

i display, in box show page users members of box.

<% @box.users.each |user| %>   <%= link_to (user.username), user %><br/> <% end %> 

i trying restrict form users not members of box not sure how write <% unless ... %> statement.

here rest of associations:

user

class user < activerecord::base   has_many :boxes   has_many :workouts, :dependent => :destroy end 

workout

class workout < activerecord::base   belongs_to :user   belongs_to :box end 

box

class box < activerecord::base   belongs_to :user   has_many :users, :through => :memberships   has_many :workouts, :through => :users   has_many :memberships end 

membership

class membership < activerecord::base   belongs_to :user   belongs_to :box end 

# membership model named_scope :for_box, lambda {|box| {:conditions => {:box_id => box.id}}}  # user model has_many :memberships  def member_of_box?(box)   !memberships.for_box(box).blank? end  # view <% unless current_user.member_of_box?(box) %>    # show form <% end %> 

disclaimer: code not tested. might need minor alterations.