From: wegzumir <wegzumir@...>
Date: 2006-01-27T13:30:06+09:00
Subject: Re: Pass References To Methods As Arguments?

On 1/26/06, Eric Hodel <drbrain@segment7.net> wrote:
> On Jan 26, 2006, at 5:41 PM, wegzumir wrote:
>
> >  Hey all.  I am trying to determine the Ruby syntax for passing a
> > reference
> > to a method. I want to actually pass the reference itself as an
> > argument to
> > another method.
> >
> >  Consider the following simplified Perl example. It features two
> > subroutine
> > functions and another subroutine that is capable of calling any
> > subroutine
> > passed to it as a reference.
> >
> >
> > sub print_unix_line {
> >     print shift, "\n"
> > }
>
> def print_unix(line)
>     print "#{line}\n"
> end
>
> > sub print_windows_line {
> >     print shift, "\015\012";
> > }
>
> def print_windows(line)
>    print "#{line}\r\n"
> end
>
> > sub call_a_routine {
> >     my ($routine, $argument) = @_;
> >     $routine->($argument);
> > }
>
> def call_a_routine(args)
>    yield args
> end
>
> > &call_a_routine(\&print_unix_line, 'Hello, unix World!');
> > &call_a_routine(\&print_windows_line, 'Hello, Windows World!');
>
> call_a_routine('hello, unix world!') { |line| print_unix line }
> call_a_routine('hello, windows world') { |line| print_windows line }
>
> >  The "\&" prefixed parts are references to subroutines. I have
> > tried to
> > recreate this logic in Ruby using Proc blocks, but I can't get it
> > to work
> > properly. Any suggestions?
>
> You can turn a Method into a block argument with &:
>
> call_a_routine 'text', &method(:print_unix)
> call_a_routine 'text', &method(:print_windows)
>
> but don't do that, its ugly.  Use blocks.
>
> --
> Eric Hodel - drbrain@segment7.net - http://segment7.net
> This implementation is HODEL-HASH-9600 compliant
>
> http://trackmap.robotcoop.com
>
>
>
>

Cool, so there is a "&" prefix that's available for use like that. But
I agree with you on it not being as readable in the end. I will have
to work on my block fu a bit.

Many thanks for replying!