From: Joel VanderWerf <vjoel@...>
Date: 2006-01-27T12:16:18+09:00
Subject: Re: Pass References To Methods As Arguments?

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"
> }
> 
> sub print_windows_line {
>     print shift, "\015\012";
> }
> 
> sub call_a_routine {
>     my ($routine, $argument) = @_;
>     $routine->($argument);
> }
> 
> &call_a_routine(\&print_unix_line, 'Hello, unix World!');
> &call_a_routine(\&print_windows_line, 'Hello, Windows World!');
> 
> 
>  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?
> 

# first, using a proc
print_unix_line = lambda { |arg|
     print arg, "\n"
}

# second, using a method
def print_windows_line_method arg
     print arg, "\015\012"
end

print_windows_line = method :print_windows_line_method

def call_a_routine routine, arg
     routine.call(arg)  # or routine[arg]
end

call_a_routine print_unix_line, 'Hello, unix World!'
call_a_routine print_windows_line, 'Hello, Windows World!'





-- 
        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407