Saving list of IDs in a :string type field?

Hello,

I'm using a session variable to store a list of IDs during a session.

Basically, a user selects many options from a group of checkboxes, and
I save that in a session variable.

When I retrieve the session variable and set a model's variable to
that value, it works fine.

For instance:

<input type="checkbox" name="user_profile[language_ids][]" value="1" /

Language 1

<input type="checkbox" name="user_profile[language_ids][]" value="2" /

Language 2

<input type="checkbox" name="user_profile[language_ids][]" value="3" /

Language 3

<input type="checkbox" name="user_profile[language_ids][]" value="4" /

Language 4

<input type="checkbox" name="user_profile[language_ids][]" value="5" /

Language 5

I set session[:language_ids] = params[:user_profile][:language_ids]

When I retrieve that:
@user_profile.language_ids = session[:language_ids]
and I save it, it works fine.

My problem is...I want to store those values in a database, but just
in 1 field.

So I created a string type field and save it. But the value looks
strange on the way out of the DB and I can't set the
@user_profile.language_ids to that value.

Is there a trick to saving this kind of a list of IDs to a DB field?

Thanks,
Andy

http://api.rubyonrails.org/classes/ActiveRecord/Base.html#M001316

serialize(attr_name, class_name = Object)

If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically. The serialization is done through YAML. If class_name is specified, the serialized object must be of that class on retrieval or SerializationTypeMismatch will be raised.
Attributes

     * attr_name - The field name that should be serialized.
     * class_name - Optional, class name that the object type should be equal to.

Example

   # Serialize a preferences attribute
   class User
     serialize :preferences
   end

You;ve got to convert it to a string. Either use serialize as Phillip
suggested or foo_ids = session[:language_ids].join(',') (and then the
corresponding split whenyou retrieve the row from the database). The
default to_s on Array doesn't do anything very useful in this case.

Fred