Rails - Dec 2006 - View: @object.send('method') vs. eval("@object.method")

All,

I have a view component that I would like to generalize.

What are the practical differences (if any) between using

@object.send(''xyz'')

and

eval("@object.xyz")

to dynamically get at an object''s attributes?

Thanks,
Wes

-- 
Posted via http://www.ruby-forum.com/.

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Wes Gamble wrote:
> All,
>
> I have a view component that I would like to generalize.
>
> What are the practical differences (if any) between using
>
> @object.send(''xyz'')
>
> and
>
> eval("@object.xyz")
>
> to dynamically get at an object''s attributes?
>
> Thanks,
> Wes
>
>   
Short answer: The first is much better from a security point of view 
(image what @object.xyz could contain). If send doesn''t have enough 
functionality, investigate instance_eval:
http://corelib.rubyonrails.org/classes/Object.html#M001079

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In this particular case, I''m just using the eval to get at attributes
of
an object, so I have complete control over what is getting
"eval"''ed.

The reason I want to use eval is if I want to get at an attribute that 
is embedded in a subordinate object.

I can specify that with x.y.z.attr and eval it

instead of

x.send(y).send(z).send(attr) or

x.instance_eval { @y.send(z).send(attr) } or other more verbose ways of 
expressing "go get this attribute from somewhere in the object graph".

Wes

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Another option could be do define the [] method on the object to return the
result of running that method.

class MyClass
  def [](method)
    send(method)
  end
end

That would make it less verbose:

  x[y][z][attr]

But if you are 100% sure that what is being passed to eval is completely
safe, then using eval shouldn''t be a problem.

-Jonathan

On 12/5/06, Wes Gamble
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
>
> In this particular case, I''m just using the eval to get at
attributes of
> an object, so I have complete control over what is getting
"eval"''ed.
>
> The reason I want to use eval is if I want to get at an attribute that
> is embedded in a subordinate object.
>
> I can specify that with x.y.z.attr and eval it
>
> instead of
>
> x.send(y).send(z).send(attr) or
>
> x.instance_eval { @y.send(z).send(attr) } or other more verbose ways of
> expressing "go get this attribute from somewhere in the object
graph".
>
> Wes
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>

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