Rails - Sep 2006 - Collection management on form updates - problem with updating

I have an AR descendant (job.rb) that contains a collection of other AR
models.

has_many :target_lists, :through => :job_list_associations, :source =>
:target_list

I have a form that I use to update the target_lists array.

Here are the two methods for "target_list_ids" which I use to manage
the form data for job.

  def target_list_ids
    ids = Array.new
    self.target_lists.each do |list|
       ids << list.DataSetID
    end
    ids
  end

  public
  def target_list_ids=(list_array)
    #self.target_lists = Array.new - WHY DOES THIS CAUSE
PROBLEMS?!!?!!?
    self.target_lists.clear
    list_array.each do |id|
      self.target_lists << TargetList.find(id)
    end
  end

On the post, when target_list_ids is called, if I use "clear" on the
target_lists array and then set whatever came in on the form,
everything works fine and I see my changes on the form.

However, if I try to assign self.target_lists to a new Array object and
do the setting, I never see the changes.  When the form redisplays
(assuming another error on the page, I see the form without any list
changes I made).

This _almost_ makes sense to me, but I wondered if someone could
explain why setting self.target_lists to be a new Array object seems to
ensure that none of the changes are stored in the job object.  Is it
because the "attribute" target_lists is not being updated when I
create
the new array?  And if I simply manipulate the existing collection (via
clear), I''m directly updating the "attribute" target_lists?

Thanks,
Wes


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Does the issue with resetting my collection to a new Array stem from the 
fact that I''m not setting the join attribute on the elements that
I''m
adding to the collection?

The thing about that is this is a _new_ Job object so there isn''t 
anything in the database, so I wouldn''t think that the absence of join 
attributes would be an issue - there shouldn''t be any foreign key
values
anyway.

WG

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