Rails - Sep 2005 - Enforce Read Only Access?

Is there a way to enforce read-only access on an ActiveRecord object? I want
to be able to modify the AR object, but I don''t want it *ever* to be
saved
to the DB.

I know there are a few ways, such as only granting that MySQL user read only
access (no inserts or updates), or I can manually override the save() method
... but I only want this to be a temporary thing. Sort of like:

ActiveRecord::Base.set_readonly

Which can then be manually reversed by

ActiveRecord::Base.set_fullaccess

Just curious. Thanks!


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Hi

You could use a callback for. Have a look here: http:// 
ar.rubyonrails.com/classes/ActiveRecord/Callbacks.html

Regards

Manuel Holtgrewe

On 29 Sep 2005, at 23:27, Belorion wrote:
> Is there a way to enforce read-only access on an ActiveRecord object?  
> I want to be able to modify the AR object, but I don''t want it
*ever*
> to be saved to the DB. 
>
>  I know there are a few ways, such as only granting that MySQL user 
> read only access (no inserts or updates), or I can manually override 
> the save() method ... but I only want this to be a temporary thing.  
> Sort of like:
>
>  ActiveRecord::Base.set_readonly
>
>  Which can then be manually reversed by
>
>  ActiveRecord::Base.set_fullaccess
Or some combination of both. Just an idea, not tried this:

def toggle_read_only

   # start as if saving is allowed
   @read_only ||= false

   #toggle read only
   @read_only = !@read_only
end

def save
   unless @read_only
	super
   else
     ... # something else here?
   end
end

	Mike

On Sep 29, 2005, at 3:27 PM, Belorion wrote:
> Is there a way to enforce read-only access on an ActiveRecord  
> object?  I want to be able to modify the AR object, but I don''t  
> want it *ever* to be saved to the DB.
The Ruby-esque way to make something immutable is via .freeze -  
though I have no idea if that''ll work with an instance of ActiveRecord.

--Steve

Stephen Waits wrote:
> 
> On Sep 29, 2005, at 3:27 PM, Belorion wrote:
> 
>> Is there a way to enforce read-only access on an ActiveRecord 
>> object?  I want to be able to modify the AR object, but I
don''t  want
>> it *ever* to be saved to the DB.
> 
> 
> The Ruby-esque way to make something immutable is via .freeze -  though
> I have no idea if that''ll work with an instance of ActiveRecord.
That''d do the opposite, surely - the AR object couldn''t be
changed, but
the save method would still work.  There are times when you''d want that
functionality, too, so I don''t think freeze should be overridden.

Quick and easy: swap out the connector for an instance of an abstract
connection adapter, so that the AR object forgets how to update the
database, or just override the save method (or create_or_update) with
something harmless.

Proper: check the role of the user at save time against a permission
field in the table.

-- 
Alex

Freeze works (I think Rails uses it on objects whose records have been 
destroyed?) and was my first thought, but Belorion wants to be able to 
change the AR object, but to interrupt any attempt to save to the 
database - so it''s the database record he wants to be ''read
only''.

On 30 Sep 2005, at 01:16, Stephen Waits wrote:
>
> On Sep 29, 2005, at 3:27 PM, Belorion wrote:
>
>> Is there a way to enforce read-only access on an ActiveRecord object? 
>>  I want to be able to modify the AR object, but I don''t want
it
>> *ever* to be saved to the DB.
>
> The Ruby-esque way to make something immutable is via .freeze - though 
> I have no idea if that''ll work with an instance of ActiveRecord.
>
> --Steve
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

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On Sep 30, 2005, at 11:36 AM, Michael Houghton wrote:
> Freeze works (I think Rails uses it on objects whose records have  
> been destroyed?) and was my first thought, but Belorion wants to be  
> able to change the AR object, but to interrupt any attempt to save  
> to the database - so it''s the database record he wants to be
''read
> only''.
Someone mentioned callbacks earlier.

# Fail fast (good)
class Foo < ActiveRecord::Base
   class ReadOnly < ActiveRecord::ActiveRecordError; end

   before_save { raise ActiveRecord::ReadOnly }
end

# Silently ignore (evil)
class Foo < ActiveRecord::Base
   before_save { false }
end

Best,
jeremy
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