Rails - Mar 2006 - Need for multiple acts_as_list

I have a model "Childmodel" that belongs_to two other models
"Parent1"
and "Parent2". "Parent1" "has_many :childmodels, :order
=> :positionp1"
and "Parent2" "has_many :childmodels, :order =>
:positionp2". i.e. The
child is independently positioned within each of its parents.

This works fine and gets me the useful methods associated with 
belongs_to and has_many. However, I would like to use acts_as_list on 
the Childmodel in order to have the order fields set when I do 
Childmodel.new.

At present, acts_as_list only works with a single parent/child 
relationship. It finds the highest-used order field in a before_create 
callback with SQL like "SELECT * FROM parent WHERE parent_id = 
#{parent_id} ORDER position DESC LIMIT 1". It adds 1 to this and stores 
it in the new record.

I am thinking I might have a go at modifying acts_as_list to support 
multiple occurrences, but first I''d be interested in people''s
thoughts
on the best API for this. For example, the method "child.move_higher" 
would have to become "child.move_higher_in_parent1" or 
"child.parent1_list.move_higher". Are there any better suggestions?

The acts_as_list method could become:

acts_as_list :parent => :parent1, :scope => :parent1_id, :column => 
:position_within_parent1

Any ideas on this gratefully received. If anyone else has a solution (or 
would like to develop one) that would be great! Also, if anyone is 
already doing this. Also, if anyone can see any logical gotchas in this 
approach.

Julian

-- 
Posted via http://www.ruby-forum.com/.

Am Mittwoch, den 22.03.2006, 11:25 +0100 schrieb Julian
Gall:
> I have a model "Childmodel" that belongs_to two other models
"Parent1"
> and "Parent2". "Parent1" "has_many :childmodels,
:order => :positionp1"
> and "Parent2" "has_many :childmodels, :order =>
:positionp2". i.e. The
> child is independently positioned within each of its parents.
> 
> This works fine and gets me the useful methods associated with 
> belongs_to and has_many. However, I would like to use acts_as_list on 
> the Childmodel in order to have the order fields set when I do 
> Childmodel.new.
> 
> At present, acts_as_list only works with a single parent/child 
> relationship. It finds the highest-used order field in a before_create 
> callback with SQL like "SELECT * FROM parent WHERE parent_id = 
> #{parent_id} ORDER position DESC LIMIT 1". It adds 1 to this and
stores
> it in the new record.
> 
> I am thinking I might have a go at modifying acts_as_list to support 
> multiple occurrences, but first I''d be interested in
people''s thoughts
> on the best API for this. For example, the method
"child.move_higher"
> would have to become "child.move_higher_in_parent1" or 
> "child.parent1_list.move_higher". Are there any better
suggestions?
> 
> The acts_as_list method could become:
> 
> acts_as_list :parent => :parent1, :scope => :parent1_id, :column
=>
> :position_within_parent1
> 
> Any ideas on this gratefully received. If anyone else has a solution (or 
> would like to develop one) that would be great! Also, if anyone is 
> already doing this. Also, if anyone can see any logical gotchas in this 
> approach.
http://wiki.rubyonrails.com/rails/pages/Acts+as+HABTM+List

-- 
Norman Timmler

http://blog.inlet-media.de

Norman Timmler wrote:
> 
> http://wiki.rubyonrails.com/rails/pages/Acts+as+HABTM+List
Thanks for that. A couple of questions.

1) Does it set the ''position'' field on record creation?
2) Do you have apointer to any documentation on writing a plugin like 
this? It would be a good approach if I create my own?

Julian

-- 
Posted via http://www.ruby-forum.com/.

Am Mittwoch, den 22.03.2006, 12:12 +0100 schrieb Julian
Gall:
> Norman Timmler wrote:
> 
> > 
> > http://wiki.rubyonrails.com/rails/pages/Acts+as+HABTM+List
> 
> Thanks for that. A couple of questions.
> 
> 1) Does it set the ''position'' field on record creation?
> 2) Do you have apointer to any documentation on writing a plugin like 
> this? It would be a good approach if I create my own?
1) It automatically sets the position field after setting the
association, means after adding to a parent. This can be at creation
time.

2) It is derived from acts_as_list. A general example how to write a
plugin can be found here:

http://wiki.rubyonrails.org/rails/pages/HowTosPlugins

Maybe you can a little bit clearer in what the functionality of
acts_as_habtm_list differs from what you want to to. Maybe you can
modify or extend the plugin.

-- 
Norman Timmler

http://blog.inlet-media.de

Norman Timmler wrote:
> Maybe you can a little bit clearer in what the functionality of
> acts_as_habtm_list differs from what you want to to.
Mainly, I need acts_as_list to work with has_many and belongs_to, rather 
than has_and_belongs_to_many.

And thanks very much for those plugin pointers. It doesn''t look too 
difficult.

Julian

-- 
Posted via http://www.ruby-forum.com/.

Could you use a family model where a user can have_many families, belong_to
family where the family has_one mother, has_one father, has_many children?

Then the children could act_as_list within the scope of the family.


On 3/22/06, Julian Gall <julian.gall@gmail.com>
wrote:
>
> Norman Timmler wrote:
>
> > Maybe you can a little bit clearer in what the functionality of
> > acts_as_habtm_list differs from what you want to to.
>
> Mainly, I need acts_as_list to work with has_many and belongs_to, rather
> than has_and_belongs_to_many.
>
> And thanks very much for those plugin pointers. It doesn''t look
too
> difficult.
>
> Julian
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Daniel ----- wrote:
> Could you use a family model where a user can have_many families, 
> belong_to
> family where the family has_one mother, has_one father, has_many 
> children?
> 
> Then the children could act_as_list within the scope of the family.
A very good example. But suppose parents remarry and one child is now 
part of another family too. I think this is where Norman''s 
acts_as_habtm_list would help, although I don''t think it would allow
for
each child to have a different position in each family.

A better example for my requirement would be a child belonging to a 
family and to a school. The family and the school list both have a 
position for the child.

Julian

-- 
Posted via http://www.ruby-forum.com/.

Am Mittwoch, den 22.03.2006, 13:48 +0100 schrieb Julian
Gall:
> Daniel ----- wrote:
> > Could you use a family model where a user can have_many families, 
> > belong_to
> > family where the family has_one mother, has_one father, has_many 
> > children?
> > 
> > Then the children could act_as_list within the scope of the family.
> 
> A very good example. But suppose parents remarry and one child is now 
> part of another family too. I think this is where Norman''s 
> acts_as_habtm_list would help, although I don''t think it would
allow for
> each child to have a different position in each family.
That is exactly what acts_as_habtm_list does! You can have multiple
parents with individual position of the child within a parent scope.

I''ll give you an example:

class Product < ActiveRecord::Base
  has_and_belongs_to :groups
  acts_as_habtm_list :scope => :groups
end

class Group < ActiveRecord::Base
  has_and_belongs_to :products
end

Each Product has it''s individual position within a Group scope, even
the
Product is assigned to multiple Groups.

-- 
Norman Timmler

http://blog.inlet-media.de

Norman Timmler wrote:
> That is exactly what acts_as_habtm_list does! You can have multiple
> parents with individual position of the child within a parent scope.
> 
> I''ll give you an example:
> 
> class Product < ActiveRecord::Base
>   has_and_belongs_to :groups
>   acts_as_habtm_list :scope => :groups
> end
> 
> class Group < ActiveRecord::Base
>   has_and_belongs_to :products
> end
> 
> Each Product has it''s individual position within a Group scope,
even the
> Product is assigned to multiple Groups.
OK. So you presumably store the position in the intermediate join table?

Julian

-- 
Posted via http://www.ruby-forum.com/.

Am Mittwoch, den 22.03.2006, 16:12 +0100 schrieb Julian
Gall:
> Norman Timmler wrote:
> > That is exactly what acts_as_habtm_list does! You can have multiple
> > parents with individual position of the child within a parent scope.
> > 
> > I''ll give you an example:
> > 
> > class Product < ActiveRecord::Base
> >   has_and_belongs_to :groups
> >   acts_as_habtm_list :scope => :groups
> > end
> > 
> > class Group < ActiveRecord::Base
> >   has_and_belongs_to :products
> > end
> > 
> > Each Product has it''s individual position within a Group
scope, even the
> > Product is assigned to multiple Groups.
> 
> OK. So you presumably store the position in the intermediate join table?
Yes. Just add the position column to your join table, the rest is done
automagically.

-- 
Norman Timmler

http://blog.inlet-media.de

I have a question about how best to setup something similiar to this. Think
of a Netflix queue, where each user has their own queue with their own
rankings of movies. In the work I am doing, everyone has the same
"movies"
in their "queue", but each is allowed to re-order their queue
separately
from each other.

The final output of this is being able to see the aggregate stack-ranking of
items in the overall queues to judge popularity of the items.

I have models for users & items, and a join table for the rankings. I
couldn''t figure out how to set the scope to multiple tables in
acts_as_list,
but thanks to this thread I see there is an option I could add for
acts_as_habtm_list.

Is this what folks here would recommend?

Many thanks,

Brian

On 3/22/06, Norman Timmler <lists@inlet-media.de>
wrote:
>
> Am Mittwoch, den 22.03.2006, 16:12 +0100 schrieb Julian Gall:
> > Norman Timmler wrote:
> > > That is exactly what acts_as_habtm_list does! You can have
multiple
> > > parents with individual position of the child within a parent
scope.
> > >
> > > I''ll give you an example:
> > >
> > > class Product < ActiveRecord::Base
> > >   has_and_belongs_to :groups
> > >   acts_as_habtm_list :scope => :groups
> > > end
> > >
> > > class Group < ActiveRecord::Base
> > >   has_and_belongs_to :products
> > > end
> > >
> > > Each Product has it''s individual position within a Group
scope, even
> the
> > > Product is assigned to multiple Groups.
> >
> > OK. So you presumably store the position in the intermediate join
table?
>
> Yes. Just add the position column to your join table, the rest is done
> automagically.
>
> --
> Norman Timmler
>
> http://blog.inlet-media.de
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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