From: Holden Glova <dsafari@...>
Date: 2002-02-02T07:05:30+09:00
Subject: Re: [GUI] Signal/slot pattern in ruby

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Sat, 02 Feb 2002 03:54, Niklas Frykholm wrote:
> I have been thinking a bit of how I would want message passing to work
> in an ideal ruby GUI.
>
> I think the signal/slot mechanism in Qt is the most elegant basic
> mechanism. (The other options are AFAIK: callbacks, observers and
> subclassing.) In a ruby GUI, signals and slots should be ordinary ruby
> functions. It should also be possible to use Proc's as slots. Like
> this:
>
> 	class Test
> 	  include Connect; extend Signal
>
> 	  attr_reader :x
> 	  signal :new_value
>
> 	  def initialize(x); @x = x; end
>
> 	  def x=(x)
> 		@x = x
> 		new_value(x)
> 	  end
> 	end
>
> 	a = Test.new(3)
> 	b = Test.new(7)
> 	a.connect(:new_value) {|i| puts "a value set to #{i}"}
> 	b.connect(:new_value) {|i| puts "b value set to #{i}"}
> 	a.connect(:new_value, b, :x=)
>
> 	a.x = 5
> 	a.disconnect(:new_value, b, :x=)
> 	a.x = 10
>
> This would produce the output:
>
> 	a value set to 5
> 	b value set to 5
> 	a value set to 10
>
> Here is my implementation of the Connect and Signal modules that make
> this happen:
>
> 	module Connect
> 	  def connect(signal, *args, &pr)
> 		@_signals = Hash.new([]) unless @_signals
> 		@_signals[signal] += if pr then [pr] else [args] end
> 	  end
>
> 	  def disconnect(signal, *args)
> 		return unless @_signals
> 		@_signals[signal].delete(args)
> 	  end
>
> 	  def activate_signal(signal, *args, &pr)
> 		return unless @_signals
> 		@_signals[signal].each {|obj, method|
> 		  if method == nil
> 			obj.call(*args, &pr)
> 		  else
> 			obj.send(method, *args, &pr)
> 		  end
> 		}
> 	  end
> 	end
>
> 	module Signal
> 	  def signal(*args)
> 		args.each {|a|
> 		  module_eval %Q{def #{a.to_s}(*args, &pr)
> 				activate_signal(#{a.inspect}, *args, &pr)
> 			end}
> 		}
> 	  end
> 	end
>
> What do you think of all this? Is there some other message passing
> mechanism that you would rather see in a ruby GUI?
>
> // Niklas

I started my GUI programming using QT and I agree that it is a nice way to 
create and use events. I could be 100% wrong, but isn't this very similar to 
what Lyle Johnson has recently done with FOX?

- -- 
Signed,
Holden Glova
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iD8DBQE8WxID+mF116Lw2cQRAseAAJ9bTPEbfJwI6DY5i32tcxD7EE+eRwCdHlQg
4RPyRFaNw34k/FOl/atD/Nk=
=R7nd
-----END PGP SIGNATURE-----