# File lib/eventmachine.rb, line 768
768:   def  EventMachine::attach io, handler=nil, *args
769:     klass = if (handler and handler.is_a?(Class))
770:       raise ArgumentError, 'must provide module or subclass of EventMachine::Connection' unless Connection > handler
771:       handler
772:     else
773:       Class.new( Connection ) {handler and include handler}
774:     end
775: 
776:     arity = klass.instance_method(:initialize).arity
777:     expected = arity >= 0 ? arity : -(arity + 1)
778:     if (arity >= 0 and args.size != expected) or (arity < 0 and args.size < expected)
779:       raise ArgumentError, "wrong number of arguments for #{klass}#initialize (#{args.size} for #{expected})"
780:     end
781: 
782:     readmode  = klass.public_instance_methods.any?{|m| m.to_sym == :notify_readable }
783:     writemode = klass.public_instance_methods.any?{|m| m.to_sym == :notify_writable }
784: 
785:     s = attach_fd io.respond_to?(:fileno) ? io.fileno : io, readmode, writemode
786: 
787:     c = klass.new s, *args
788:     @conns[s] = c
789:     block_given? and yield c
790:     c
791:   end