Has_many :through updates on delete

Rails
1

I have a model that looks like this:

class Actor < ActiveRecord::Base
has_many :member_groups, :foreign_key => ‘member_id’, :class_name =>
‘GroupMember’
has_many :groups, :through => :member_groups, :source => :group
end

class Group < Actor
has_many :group_members, :foreign_key => ‘group_id’,:dependent =>
:destroy
has_many :members, :through => :group_members, :source => :member
end

class GroupMember < ActiveRecord::Base
belongs_to :group
belongs_to :member, :class_name => ‘Actor’, :foreign_key =>
‘member_id’
belongs_to :source_group, :class_name => ‘Group’, :foreign_key =>
‘source_group_id’
end

Now, when removing a member from a Group (in the method
Group.remove_member), I need to delete a particular GroupMember instance
so I call group_members.delete(group_member). Fine so far, except that
the “has_many :through” association ‘members’ doesn’t get updated! It
seems to have retained the cached @members value and doesn’t refresh the
association (I can verify that the entry is missing from ‘group_members’
and the row has been deleted from the ‘group_members’ table. How can I
ensure that ‘members’ is updated here? I need to pass those unit tests!

2

Lee I. wrote:

Now, when removing a member from a Group (in the method
Group.remove_member), I need to delete a particular GroupMember instance
so I call group_members.delete(group_member). Fine so far, except that
the “has_many :through” association ‘members’ doesn’t get updated! It
seems to have retained the cached @members value and doesn’t refresh the
association (I can verify that the entry is missing from ‘group_members’
and the row has been deleted from the ‘group_members’ table. How can I
ensure that ‘members’ is updated here? I need to pass those unit tests!

You can always force any association to reload its cached objects by
sending its accessor with an argument of true.

group.members(true)

Give that a shot.

–
Josh S.
http://blog.hasmanythrough.com

3

On Thu, Jun 08, 2006 at 08:39:29AM +0200, Josh S. wrote:

You can always force any association to reload its cached objects by
sending its accessor with an argument of true.

group.members(true)

Give that a shot.

It actually doesn’t have to be ‘true’. Anything that is boolean true
is sufficient. I would recommend using the :reload symbol, as it is more
intention revealing.

group.members(:reload)

marcel

4

Marcel Molina Jr. wrote:

and the row has been deleted from the ‘group_members’ table. How can I
It actually doesn’t have to be ‘true’. Anything that is boolean true
is sufficient. I would recommend using the :reload symbol, as it is more
intention revealing.

group.members(:reload)

OK, but shouldn’t this “do the right thing?”. These associations are
tied by the :through reference. I assume that just as a create on the
join table will update both, so should a delete. Is this a bug?