From: Robert Klemme <shortcutter@...>
Date: 2005-09-04T00:25:28+09:00
Subject: Re: Lexical Casts with Ruby

2005/9/3, R�diger Sonderfeld <kingruedi@c-plusplus.de>:
> 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 attribute
> type can only be determined at runtime.
> 
> Is there a way for lexical casts between types in Ruby? Something like
> convert("10", Fixnum)
> => 10

Well, there are several options:

You can use send, like your_string.send(:to_i) where you determine the
symbol (:to_i, :to_f etc) at runtime.

You can use case

result = case your_string
  when /^\d+$/ then your_string.to_i
  when /^\d.\.\d+/ then your_string.to_f
  else your_string
end

Or you put conversions into a map

conv = {
Fixnum => lambda {|x| x.to_i},
Float => lambda {|x| x.to_f},
}

result = conv[Fixnum][your_string]

Hope, that gets you started.

Kind regards

robert