From: Gavin Kistner <gavin@...>
Date: 2004-09-28T12:56:25+09:00
Subject: Binding of the Caller (redux)

I'm trying to use Florian's Binding.of_caller, and it ain't working. In 
the code below, if I uncomment the Binding.of_caller line, I get the 
error:

./libs/binding_of_caller.rb:61:in `of_caller': Binding.of_caller used 
in non-method context or trailing statements of method using it aren't 
in the block. (ArgumentError)

Is there a better way to automatically store a reference to the method 
which invoked the current method? If not, can someone see what might be 
wrong? (I'd like to remove the second parameter from #dispatch_event.)


#!/usr/local/bin/ruby

require 'libs/binding_of_caller'

module EventTarget
	def add_event_listener( name, callback )
		callbacks = ((@registered_events ||= {})[ name.to_s ] ||= []);
		callbacks.delete( callback )
		callbacks << callback
	end
	def dispatch_event( evt, source )
		callbacks = (@registered_events ||= {})[ evt.name ];
		return unless callbacks
		#evt.source = Binding.of_caller{ |b| eval("self", b) }
		evt.source = source
		callbacks.each{ |m|
			m.call( evt )
		}
	end
end

class Event
	attr_accessor :name, :source, :change
	def initialize( name, change=nil )
		@name = name.to_s
		@change = change
	end
end

class HTMLInput
	include EventTarget
	
	attr_reader :value
	def value=( v )
		@value = v
		evt = Event.new( 'change', v )
		dispatch_event( evt, self )
	end
end

inp = HTMLInput.new
inp.add_event_listener( 'change', Proc.new{ |e| puts "#{e.source} just 
changed." } )
inp.add_event_listener( 'change', Proc.new{ |e| puts "The new value is 
#{e.change}." } )
inp.value = 12

#=> #<HTMLInput:0x1c58e4> just changed.
#=> The new value is 12


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