From: "David A. Black" <dblack@...>
Date: 2005-09-04T00:35:37+09:00
Subject: Re: Lexical Casts with Ruby

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Hi --

On Sun, 4 Sep 2005, [utf-8] R=C3=BCdiger Sonderfeld wrote:

> Hello,
> I want to assign some values I recive in string form to attributes of a
> user specified class. The problem is that I have to lexical cast the
> strings into the required type. I can't use to_i or to_f because the attr=
ibute
> type can only be determined at runtime.
>
> Is there a way for lexical casts between types in Ruby? Something like
> convert("10", Fixnum)
> =3D> 10

See Robert's answer.  Also, another possibility would be to put the
knowledge directly in the object:

   class MyClass
     def x=3D(s)
       @x =3D s.to_i
     end

     def y=3D(s)
       @y =3D s.to_f
     end

     # ...
   end

That way, you can just do:

   obj.x =3D "10"

and have the conversion be encapsulated in the object.

If using the assignment syntax seems *too* transparent (since you're
not really setting it to "10"), you could use differently-named
methods.  But the principle would be the same: put the knowledge in
the object.


David

--=20
David A. Black
dblack@wobblini.net
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