From: Trans <transfire@...>
Date: 2006-12-21T20:36:57+09:00
Subject: Re: Assignment method strangeness


Ryan Williams wrote:
> >
> > As you can see in the first one.. even a single value passed to an
> > assignment is parsed as an array. If you need multiple arguments to an
> > assignment, you have to handle them inside the method body itself.
> >
> >
> You are correct.  That's pretty useful, though you still can't pass in
> blocks.
>
> The reason I was interested in this was that I wanted to create some
> attributes that could be assigned either a literal value, or a block that
> returned the literal value when called.  Then you could do some really lazy
> evaluation, as in:
>
> test.a = { long_computation }
> ....
> ...in another scope...
> ....
> test.a   # returns result of computation
>
> Or you could use it to keep some objects in sync:
>
> test.a = { some_other_object.b }
> some_other_object.b = 42
> test.a = 42
>
> I guess the best route to this is either a new assignment-like method (
> test.set_a) or test.a = Proc.new.

  class Test
    def a=(x)
      case x
      when Proc
         puts "proc!"
      else
         puts "value"
      end
    end
  end

  test = Test.new
  test.a = lamba { some_other_object.b }

also if you do need more than one arg:

  def a(x=Exception, y=nil)
    return @a if x == Exception
    @a = x + y  # or whatever
  end

t.