From: Ross Shaw <rshaw1961@...>
Date: 2001-05-02T20:41:23+09:00
Subject: [ruby-talk:14540] Re: Named parameters: Bright idea fizzles


"Hal E. Fulton" <hal9000@hypermetrics.com> wrote in message
news:00b601c0d2b3$5c993fa0$01f9fea9@austin.rr.com...
> One day, a semi-intelligent caveman named Hal
> was thinking to himself about named parameters
> in Ruby.
>
> He knew about the hash trick, but felt a primitive
> longing for something more.
>
> He also knew about Named Parameters in a
> Later Version of Ruby, but he hadn't caught onto
> the "passage of time" concept yet.
>
> "Uh," he grunted as a ten-watt light-bulb appeared
> over his head. "I'll just do it this way, using
> instance_eval and a block."
>
>   def myfunc(&block)
>     instance_eval(&block)
>     puts "#{a}  #{b}  #{c}"
>   end
>
>   myfunc {a = 3; b = 5; c = 7 }
>

All the variables in your block will only be local within the block and
therefore undefined outside the block. Make them instance variables and you
will be right.

  def myfunc(&block)
    instance_eval(&block)
    puts "#{@a}  #{@b}  #{@c}"
  end

  myfunc {@a = 3; @b = 5; @c = 7 }   ==>  3 5 7


Alternatively you can pass in a string to eval so it would be as below:

  def myfunc(eval_string)
    eval(eval_string)
    puts "#{a}  #{b}  #{c}"
  end

  myfunc ("a = 3; b = 5; c = 7")   ==> 3 5 7


I suspect the first is what you want to do.

Ross