Rails - May 2007 - Dynamically iterate around a table's columns (using content_columns?) to save some fields

Hi there,
I was trying to make some DRY code in the ''edit'' controller so
it will
check for every single column and if it is empty, to write something
like ''[Undefined]'' in it''s place. The thing is
didn''t want to make the
code static and have to rewrite it every time i change the table it
uses, so i thought that this (or something like this) would work:

  def edit
    @post = Post.find(params[:id])
    for column in Post.content_columns
	    if @post.column = ''''
		    @post.column = "[#{column.human_name} not set]"
	    end
    end
  end

Also, i found weird the fact that (in other cases not here - as this
code won''t work) if i use the condition @post.<some_column_here>
= nil
doesn''t seem to work (when the selected column is null, meaning not
set in model creation). Instead i used the = '''' (an empty
sting) and
worked ok until now, but i believe that this is reaaally bad coding
and a hole of bugs in the future...
Isn''t there any better way to make this work?

Any help would be highly appreciated :)

P.S. : As you can see (probably) i''m pretty noob in rails when it
comes to practical experience, although i''ve read a lot documentation
and books about rails (and ruby).


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> Also, i found weird the fact that (in other cases not here - as this
> code won''t work) if i use the condition
@post.<some_column_here> = nil
> doesn''t seem to work (when the selected column is null, meaning
not
> set in model creation). Instead i used the = '''' (an empty
sting) and
> worked ok until now, but i believe that this is reaaally bad coding
> and a hole of bugs in the future...
> Isn''t there any better way to make this work?
i found out why this is happening so nevermind about this one. stupid
scaffolding....


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Glad you figured it out. Couple thoughts to chew on though:

"@post.column" would not use the contents of the variable
"column" to
look for a column with that name... it  tries to call a "column"
method
on the object @post.

Also, the logic determining whether a model gets some default value 
should really be in the model.... and then you can use the protected 
"write_attribute" method, perhaps in one of the lifecycle callbacks.

b

demisone wrote:
> 
>> Also, i found weird the fact that (in other cases not here - as this
>> code won''t work) if i use the condition
@post.<some_column_here> = nil
>> doesn''t seem to work (when the selected column is null,
meaning not
>> set in model creation). Instead i used the = '''' (an
empty sting) and
>> worked ok until now, but i believe that this is reaaally bad coding
>> and a hole of bugs in the future...
>> Isn''t there any better way to make this work?
> 
> i found out why this is happening so nevermind about this one. stupid
> scaffolding....
> 
> 
> > 
> 
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I have been trying to do the same thing.
What I ended doing is the following. I would be interested to find out
if I have offended many guidelines in doing so.

I moved the code to loop on the table column in the model itself and
used the @attributes hash directly to access the columns.

[''col1'',''col2'',''col3''].each
{|col| @attributes[col]=params[col]}

I never got something like self.#{col} to work.

For now, I am happy with using @attributes[var]. Does anyone have a
better solution?

J-F (Ottawa,Canada)



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> I moved the code to loop on the table column in the model itself and
> used the @attributes hash directly to access the columns.
>
>
[''col1'',''col2'',''col3''].each
{|col| @attributes[col]=params[col]}
You mean you write [''col1'',...,] statically? That''s
no good for what i
wanted to to... :(
> I never got something like self.#{col} to work.
Yeah, me neither :D
> For now, I am happy with using @attributes[var]. Does anyone have a
> better solution?
I''m not aware of this (i think), gonna check it out...

Thanks for sharing your thoughts anyway :)

-Nikos D (Athens, Greece)


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I think what you want to code is :

     post[column]

This uses the [] accessor method and treats ''column'' as a
variable and
thus gets the correct (dynamic) column that you want to process.

HTH...jon

On May 6, 10:05 am, "Nikos D."
<demis...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> > I moved the code to loop on the table column in the model itself and
> > used the @attributes hash directly to access the columns.
>
> >
[''col1'',''col2'',''col3''].each
{|col| @attributes[col]=params[col]}
>
> You mean you write [''col1'',...,] statically?
That''s no good for what i
> wanted to to... :(
>
> > I never got something like self.#{col} to work.
>
> Yeah, me neither :D
>
> > For now, I am happy with using @attributes[var]. Does anyone have a
> > better solution?
>
> I''m not aware of this (i think), gonna check it out...
>
> Thanks for sharing your thoughts anyway :)
>
> -Nikos D (Athens, Greece)

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