Betternestedset talk - Aug 2007 - Reason why should #parent_id=(x) raise an exception?

Hi all,

Can someone explain to me the reasoning behind the current
implementation of the attribute writer for the parent_id column in a
nested set object? At the moment it just throws an error:

def #{acts_as_nested_set_options[:parent_column]}=(x)
 raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to
      #{acts_as_nested_set_options[:parent_column]}: it''s an internal
field handled by   acts_as_nested_set code, use move_to_* methods
instead."
end


Would it not have been possible to define it as something like this:

def #{acts_as_nested_set_options[:parent_column]}=(x)
       move_to_child_of(x)
end

?

If the above could work, it would allow you to do bulk assignment to
the parent_id attribute safely, which would save typing a few lines
in controller code... but maybe I''m missing something!

thanks,

Brian

Hi,

Le 1 ao?t 07 ? 14:39, Brian Sheehan a ?crit :
> Can someone explain to me the reasoning behind the current
> implementation of the attribute writer for the parent_id column in a
> nested set object? At the moment it just throws an error:
>
> def #{acts_as_nested_set_options[:parent_column]}=(x)
>  raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to
>       #{acts_as_nested_set_options[:parent_column]}: it''s an
internal
> field handled by   acts_as_nested_set code, use move_to_* methods
> instead."
> end
>
>
> Would it not have been possible to define it as something like this:
>
> def #{acts_as_nested_set_options[:parent_column]}=(x)
>        move_to_child_of(x)
> end
There are two reasons:
1. we don''t know if it should be the first or the last child of the  
new parent
2. more importantly, setting a value in AR objects in rails never  
makes an automatic save of the object instance. Here move_to_child  
changes not only db values for the current object, but for many  
others. That''s why we think it better not to have a simple method to  
achieve this change.
But feel free to alter this behaviour in your copy if you think it''s  
safe for you !

Jean-Christophe Michel
--
symetrie.com

Better Nested Set for rails:
http://opensource.symetrie.com/trac/better_nested_set

Hi Jean-Christophe,

That makes sense, thank you!

Brian


On 8/1/07, Jean-Christophe Michel <jc.michel at symetrie.com>
wrote:
> Hi,
>
> Le 1 ao?t 07 ? 14:39, Brian Sheehan a ?crit :
> > Can someone explain to me the reasoning behind the current
> > implementation of the attribute writer for the parent_id column in a
> > nested set object? At the moment it just throws an error:
> >
> > def #{acts_as_nested_set_options[:parent_column]}=(x)
> >  raise ActiveRecord::ActiveRecordError, "Unauthorized assignment
to
> >       #{acts_as_nested_set_options[:parent_column]}: it''s an
internal
> > field handled by   acts_as_nested_set code, use move_to_* methods
> > instead."
> > end
> >
> >
> > Would it not have been possible to define it as something like this:
> >
> > def #{acts_as_nested_set_options[:parent_column]}=(x)
> >        move_to_child_of(x)
> > end
>
> There are two reasons:
> 1. we don''t know if it should be the first or the last child of
the
> new parent
> 2. more importantly, setting a value in AR objects in rails never
> makes an automatic save of the object instance. Here move_to_child
> changes not only db values for the current object, but for many
> others. That''s why we think it better not to have a simple method
to
> achieve this change.
> But feel free to alter this behaviour in your copy if you think
it''s
> safe for you !
>
> Jean-Christophe Michel
> --
> symetrie.com
>
> Better Nested Set for rails:
> http://opensource.symetrie.com/trac/better_nested_set
>
>
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