Rails - Oct 2006 - Multi-selects and many-to-many relationships.

Hello,
So far I''ve been making selects in the form that end being
automatically
mapped to the relationship one-to-many on the database.
Now I am trying to make a multi-select that maps to a many-to-many 
relationship. Is that possible ?
I have Courses and Books, many to many. So, when editing a book I output:

<%= select ''book'', ''courses'',
Course.find(:all, :order => :name).collect {|p|
[ p.name, p.id ] }, {:include_blank => true}, {:class 
=> "text-input", :multiple => true, :size => 10 }   %>

It prints correctly, but when saving I get "Course expected, got
String". I''ve
tried with ''course_ids'' instead of ''courses''
but then I get "undefined method
`course_ids'' for #<Book:0xb6eabf94>" when generating the
form.

How should I do it ?

Thank you.
-- 
Pupeno <pupeno-GAtDADarczzQT0dZR+AlfA@public.gmane.org>
(http://pupeno.com)

Pupeno wrote:
> Hello,
> So far I''ve been making selects in the form that end being
automatically
> mapped to the relationship one-to-many on the database.
> Now I am trying to make a multi-select that maps to a many-to-many 
> relationship. Is that possible ?
> I have Courses and Books, many to many. So, when editing a book I output:
> 
> <%= select ''book'', ''courses'',
Course.find(:all, :order => :name).collect {|p|
> [ p.name, p.id ] }, {:include_blank => true}, {:class 
> => "text-input", :multiple => true, :size => 10 }  
%>
> 
> It prints correctly, but when saving I get "Course expected, got
String". I''ve
> tried with ''course_ids'' instead of
''courses'' but then I get "undefined method
> `course_ids'' for #<Book:0xb6eabf94>" when generating
the form.
> 
> How should I do it ?
Yes, association collections should be defining a getter as well as a setter
for the _ids method.  You can add one manually:

def course_ids
   courses.map(&:id)
end

-- 
We develop, watch us RoR, in numbers too big to ignore.


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