Question

With the following models:

class Location < ActiveRecord::Base
  has_many        :group_locations
  has_many        :groups, :through => :group_locations
  accepts_nested_attributes_for :group_locations
end

class GroupLocation < ActiveRecord::Base
  belongs_to  :group
  belongs_to  :location
end

class Group < ActiveRecord::Base
  has_many        :group_locations
  has_many        :locations, :through => :group_locations
end

the following commands in rails console does not update the associated records:

>> l = Location.find(1)
=> #<Location id: 1, phone: "[phone]", ... created_at: "2011-06-02 00:58:07",
updated_at: "2011-06-07 23:57:32">

\>\> l.group_locations
=> [#<GroupLocation group_id: 4, location_id: 1, created_at: "2011-06-02 00:58:07",
updated_at: "2011-06-02 00:58:07">, #<GroupLocation group_id: **37**, location_id: 1,
created_at: "2011-06-02 00:58:07", updated_at: "2011-06-02 00:58:07">]

>> l.update_attributes(:phone => "[phone]", :group_locations_attributes =>
[{:group_id => 4, :location_id => 1}, {:group_id => **38**, :location_id => 1}])
=> true

>> l
=> #<Location id: 1, phone: "[phone]", ... created_at: "2011-06-02 00:58:07",
updated_at: "2011-06-08 02:05:00">

>> l.group_locations
=> [#<GroupLocation group_id: 4, location_id: 1, created_at: "2011-06-02 00:58:07",
updated_at: "2011-06-02 00:58:07">, #<GroupLocation group_id: **37**, location_id: 1,
created_at: "2011-06-02 00:58:07", updated_at: "2011-06-02 00:58:07">]

Note that the update_attributes call attempts to change the second GroupLocation to have group_id = 38, but the change is not made (even though the phone number did change). After looking at the code generated when this was implemented in the controller and view, changing the array to a hash (which is what is created in that case) has no different results (and the form/controller) have the same effect of not updating the associated records even though the main record is updated.

Any idea what I need to do to get the nested attributes to update?

Answer 1

The actual answer is that the nested attributes must be accessible via attr_accessible. “accepts_nested_attributes” will only do what I want if it is accompanied by “attr_accessible :group_locations”.