Rails - Aug 2006 - multiple habtm joins on the same two tables

i have a taskmanager type of project that i am working on, where i need 
to separate joins on the same two tables. i need one join for users that 
are assigned to the task, and another join for who has read the task, so 
they can tell which ones are new.

any suggestions on the best way to accomplish this?

thanks

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Hi Josh,

I think you might be able to model this with has_many :through either one
Model (e.g. UserTaskRelation with two flags: ''read'' and
''assigned'' in it) or
two Models ''Reading'', ''Assignation''
User has_many :tasks, :through => :reading
User has_many :tasks, :through => :assignation

with the second approach you are able with the standard created_at,
updated_at to tell when a user did a reading or has been assigned to a task.

Cheers,
Jan
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Jan Prill wrote:
> Hi Josh,
> 
> I think you might be able to model this with has_many :through either 
> one
> Model (e.g. UserTaskRelation with two flags: ''read'' and
''assigned'' in
> it) or
> two Models ''Reading'', ''Assignation''
> User has_many :tasks, :through => :reading
> User has_many :tasks, :through => :assignation
> 
> with the second approach you are able with the standard created_at,
> updated_at to tell when a user did a reading or has been assigned to a 
> task.
> 
> Cheers,
> Jan
thanks for the help

what about the database schema? should the link tables be reading_tasks 
and assignation_tasks for those conventions to work?

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Hi Josh,

no for the through association you don''t need a solely join table of
the
kind of comments_posts. Instead you''ve got a full featured model (and
its
underlying table like ''readings'') wich might grow with your
application and
it''s growing needs and is even able to be handled in the great way of
the so
called restful or crud controllers. Do a little research on ''has_many
:through'' as well as restful and you''ll get the idea. HABTM
has it''s use
cases but a full ''through-model'' has so many advantages
especially for cases
like yours.

Cheers,
Jan

On 8/7/06, Josh Kieschnick <jjkiesch@gmail.com>
wrote:
>
> Jan Prill wrote:
> > Hi Josh,
> >
> > I think you might be able to model this with has_many :through either
> > one
> > Model (e.g. UserTaskRelation with two flags: ''read''
and ''assigned'' in
> > it) or
> > two Models ''Reading'',
''Assignation''
> > User has_many :tasks, :through => :reading
> > User has_many :tasks, :through => :assignation
> >
> > with the second approach you are able with the standard created_at,
> > updated_at to tell when a user did a reading or has been assigned to a
> > task.
> >
> > Cheers,
> > Jan
>
> thanks for the help
>
> what about the database schema? should the link tables be reading_tasks
> and assignation_tasks for those conventions to work?
>
> --
> 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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Jan Prill wrote:
> Hi Josh,
> 
> I think you might be able to model this with has_many :through either 
> one
> Model (e.g. UserTaskRelation with two flags: ''read'' and
''assigned'' in
> it) or
> two Models ''Reading'', ''Assignation''
> User has_many :tasks, :through => :reading
> User has_many :tasks, :through => :assignation
> 
> with the second approach you are able with the standard created_at,
> updated_at to tell when a user did a reading or has been assigned to a 
> task.
This is sort of backwards.  I think you want to have one join model and 
two associations going through it.

User:
  has_many :assignments
  has_many :assigned_tasks, :through => :assignments, :class_name => 
"Task"
  has_many :read_tasks, :through => :assignments, :class_name =>
"Task"

You can read more about this approach here:
http://blog.hasmanythrough.com/articles/2006/05/06/through_gets_uniq

--
Josh Susser
http://blog.hasmanythrough.com/

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