From: Eric Hodel <drbrain@...7.net>
Date: 2006-01-27T12:15:30+09:00
Subject: Re: Pass References To Methods As Arguments?

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
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