From: Marc Heiler <shevegen@...>
Date: 2011-12-08T17:06:32+09:00
Subject: Using any trick to omit () in constant lookup?

Hi.

I once had the idea of an abstracted UI language.

My first attempt was to do something like:

  Button.new

And convert the Button to the specific toolkit in
question - i.e. GTK Button, QT Button and so on.

This was not really possible, at least not for me.

When you have:

  class Button

Then ruby does not allow you to change that object
lateron. In other words, it will always be of class
Button, and never of class Gtk::Button, which I would
need in order to make an abstracted toolkit.

Lately I had another idea. I could simply try to
trick Ruby.

def Button
  # Do something here, decide which toolkit to
  # use, then return that.


It would then allow me to do something like:

  use :gtk

  Button.new

The interface logic would be described only once
and then be valid no matter which toolkit would
be used, within reason. (I am more interested in
finding a common base within all toolkits, and
using specialized solutions within that toolkit
only lateron.)

I could then switch to qt like this:

  use :qt



Ok, I tried a first proof of concept but failed.

--------------------------------------

require 'gtk2'

$use_gtk = true

def Button
  if $use_gtk
    return Gtk::Button
  else # else use something else.
  end
end

x = Button.new
puts x.class

--------------------------------------

^^^^^ The above code does not work. It stops with an
error like this here:

  uninitialized constant Button (NameError)

It works however when I change the line to:

  x = Button().new

But this is ugly. I don't think I want to use that,
it does not please my eyes.


Is there a way to tell ruby to change its behaviour
and treat Button not as a constant, but instead as
a method invocation call where the () parens are
omitted?

I think if I would have that option, I could write a
cross UI DSL "language".

For any more ideas I am quite happy too. My ultimate
goal is to actually use just ONE way to describe ALL
User Interface elements, including the WWW. Be it
in Ruby, or with an abstract interface language that
has to be parsed, does not matter that much to me.

Though using Ruby directly would simplify my life
of course.

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