Rails - Mar 2007 - ActiveRecord attributes -- strange behavior when adding Array to an element

Hi,

I have a database table and associated ActiveRecord model. I was
trying to store (temporarily) an array in one of the attribute
elements - not to save it, but just so that I can keep some form data
in a sensible place. A stripped down version of the problem I''m having
is:

p = Property.new(:bedroom_count => ["2","3"])
puts p.inspect # ==> will correctly show that the array is stored in
the attributes "hash"
puts p.bedroom_count # => returns 1

I realize I''m a little "off rails" on this approach, but does
anyone
have any knowledge of what''s going on in this case?

Thanks,

Steve


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On Mar 30, 2007, at 1:40 AM, Steve Midgley wrote:
> I have a database table and associated ActiveRecord model. I was
> trying to store (temporarily) an array in one of the attribute
> elements - not to save it, but just so that I can keep some form data
> in a sensible place. A stripped down version of the problem I''m
having
> is:
>
> p = Property.new(:bedroom_count => ["2","3"])
> puts p.inspect # ==> will correctly show that the array is stored in
> the attributes "hash"
> puts p.bedroom_count # => returns 1
>
> I realize I''m a little "off rails" on this approach, but
does anyone
> have any knowledge of what''s going on in this case?
The behaviour you are seeing comes from the fact that the generated  
getters call to ActiveRecord::ConnectionAdapters::Column#type_cast  
via ActiveRecord::Base#read_attribute:

   def read_attribute(attr_name)
     attr_name = attr_name.to_s
     if !(value = @attributes[attr_name]).nil?
       if column = column_for_attribute(attr_name)
         if unserializable_attribute?(attr_name, column)
           unserialize_attribute(attr_name)
         else
           column.type_cast(value)
         end
       else
         value
       end
     else
       nil
     end
   end

Note that this is an attribute reader, and so does not reset the  
underlying value. Thus, you can always get the original object using

   p.bedroom_count_before_typecast

Once understood, assigning an array to a field that is supposed to  
hold an integer is really suspicious, does it really make sense in  
your context?

-- fxn


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