Ruby Forum Ruby on Rails > What i do if i have a table with a column named "type"?

Hi everybody!

The class ActiveRecord::Base have a atribute named type and if my
table have a column with the same name i get an error if i use
model.finde, model.save and more...

I dont know what i can do to solve this problem!

Someone know?


Thanks

Noel R. Morais wrote:
> The class ActiveRecord::Base have a atribute named type and if my
> table have a column with the same name i get an error if i use
> model.finde, model.save and more...
> 
> I dont know what i can do to solve this problem!

http://rubyonrails.org/api/classes/ActiveRecord/Base.html#M000879

Put this in your model class:

def inheritance_column
  "something_other_than_type"
end

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

Hi Noel,

Noel R. Morais
>
> The class ActiveRecord::Base have a atribute named type and if my table 
> have a column with the same name i get an error if i use
> model.finde, model.save and more...
>
> I dont know what i can do to solve this problem!

You cannot have a column named 'type' and use RoR.  It is a Magic Field 
Name
( http://wiki.rubyonrails.com/rails/pages/MagicFieldNames )

>From that page...
"Rails values convention over configuration. This is also true in the 
realm
of table design where fields given particular names automatically gain
certain behaviours."

hth,
Bill

On 1-Jun-06, at 2:26 PM, Josh Susser wrote:

>
> def inheritance_column
>   "something_other_than_type"
> end
>

Sorry but that's not the way to go.  The inheritance_column method is
a *class* method.

Regardless, I believe the correct call is set_inheritance_column.  I.e.:

class MyModel < ActiveRecord::Base
   set_inheritance_column :ruby_type
end

However, if you want to access the value for the 'type' field in your
table you can't do:

model.type

you have to use:

model[:type]

All in all, if you can avoid it then don't have a column called
"type".  I don't even use it for STI - a while back I picked up a
habit of always setting the inheritance column to be 'ruby_type'.

That way I can do model.type() to get back the class object and
model.ruby_type (and model.ruby_type=) to access the string
representation of the class name.

HTH,
Trevor
--
Trevor Squires
http://somethinglearned.com

Trevor Squires wrote:
> On 1-Jun-06, at 2:26 PM, Josh Susser wrote:
> 
>>
>> def inheritance_column
>>   "something_other_than_type"
>> end
>>
> 
> Sorry but that's not the way to go.  The inheritance_column method is
> a *class* method.
> 
> Regardless, I believe the correct call is set_inheritance_column.  I.e.:
> 
> class MyModel < ActiveRecord::Base
>    set_inheritance_column :ruby_type
> end
> 
> However, if you want to access the value for the 'type' field in your
> table you can't do:
> 
> model.type
> 
> you have to use:
> 
> model[:type]
> 
> All in all, if you can avoid it then don't have a column called
> "type".  I don't even use it for STI - a while back I picked up a
> habit of always setting the inheritance column to be 'ruby_type'.
> 
> That way I can do model.type() to get back the class object and
> model.ruby_type (and model.ruby_type=) to access the string
> representation of the class name.

Thanks, Trevor.  That's a great explanation. I was just going off the 
docs, as I never have needed a field named "type" myself. You up for 
fixing the docs for #inheritance_column that say it can be overridden in 
a sublcass? :-)

I hear that "type" is eventually going to stop being a magic word in 
Ruby. Kinnehora!

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