From: Massimiliano Mirra <list@...>
Date: 2002-02-02T07:34:00+09:00
Subject: Re: [GUI] Signal/slot pattern in ruby

On Fri, Feb 01, 2002 at 11:54:49PM +0900, 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:

The following code I wrote a while ago when needing something uniform
with GTK is very similar.  It supports more than one event handler for
a given event like GTK, but doesn't support disconnecting (didn't need
that).


module Signal
  def signal_connect(sigstr, &block)
    @handlers ||= {}

    unless @handlers[sigstr]
      array = []
      def array.call(*args)
	each {|handler| handler.call(*args)}
      end
      @handlers[sigstr] = array
    end

    @handlers[sigstr].push block
  end

  def sighandle(sigstr, *args)
    if @handlers
      @handlers[sigstr].call(*args) unless @handlers[sigstr].nil?
    end
  end
end


if __FILE__ == $0
  class Test
    include Signal
    def foo
      sighandle("foo_event", 2)
    end    
  end

  t = Test.new
  t.signal_connect('foo_event') {puts "event called"}
  t.signal_connect('foo_event') {|param| puts "second handler, using the passed param: #{param}"}

  # do whatever you want here

  t.foo
end


Massimiliano