Rails - Oct 2005 - Read only model attributes

Can I somehow setup a Model so that I can prevent a
column from being updated aka a read only attribute?  
I''m thinking that I need to override the "=" operator
in my Model class.  Am I on the right track?

scott.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Scott F. Walterscottwalter.com --explorer
what''s new

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On Oct 27, 2005, at 2:14 PM, Scott Walter wrote:
> Can I somehow setup a Model so that I can prevent a
> column from being updated aka a read only attribute?
> I''m thinking that I need to override the "=" operator
> in my Model class.  Am I on the right track?
Yup!

class Foo
   def bar=(value)
     raise "I''m read-only dammit!"
   end
end

Also see the new :readonly option to find, which makes the entire  
record read-only.

begin
   f = Foo.find(:first, :readonly => true)
   f.save
rescue ActiveRecord::ReadOnlyRecord
   puts "Look, but don''t touch!  Thx."
end

Best,
jeremy
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Jeremy Kemper wrote:
> Yup!
> 
> class Foo
>   def bar=(value)
>     raise "I''m read-only dammit!"
>   end
> end
I''ve got a question about something related. When you override the
"=" operator
like this, is it still necessary to protect against mass assignments with 
"attr_protected"? In other words, does assigning like
"model.attributes = hash"
use the "=" operator, or does it generate SQL itself?

I''m pretty sure it is the former, but thought I''d ask, just to
be sure.

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On Oct 27, 2005, at 3:38 PM, Wiebe Cazemier wrote:
> Jeremy Kemper wrote:
>> Yup!
>> class Foo
>>   def bar=(value)
>>     raise "I''m read-only dammit!"
>>   end
>> end
>>
>
> I''ve got a question about something related. When you override the
> "=" operator like this, is it still necessary to protect against
> mass assignments with "attr_protected"? In other words, does  
> assigning like "model.attributes = hash" use the "="
operator, or
> does it generate SQL itself?
>
> I''m pretty sure it is the former, but thought I''d ask,
just to be
> sure.
Yes, attributes= calls each attr_name= method rather than setting the  
hash directly.

To match attr_protected behavior, you''d drop the value on the floor  
instead of raising an exception:

class Foo
   # Ignore attempts to set bar.
   def bar=(value) end
end

jeremy
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