Re: Re: Re: passing arguments in a dispatch table

You say "Frankly, I think I need an object, but I'm reluctant to use one or a closure.", but you're using closures in your code segment above.

You might want to consider this approach:

    my $dispatch = {
        1   => sub { search_menu() },
        2   => sub { my $book = shift; edit_name($book) },
        3   => sub { my $book = shift; add_entry($book) },
        4   => sub { my $book = shift; delete_entry($book) },
        5   => sub { save_default() },
        6   => sub { print "Goodbye!\n"; exit },
        e   => sub { print "Goodbye!\n"; exit }
    };
    sub process {
        my ( $choice, $book ) = @_;
        print $dispatch->{$choice}->($book);
    }
[download]

Here, we're removing the closure completely, and passing the args directly to the appropriate sub. Did I completely miss what you're trying to do?

Comment on Re: Re: Re: passing arguments in a dispatch table Download Code

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Re: Re: Re: Re: passing arguments in a dispatch table by CharlesClarkson (Curate) on Apr 29, 2002 at 06:06 UTC
I have two problems with this aproach `$dispatch` is not passed to `process`, making it a global variable. Just what I'd like to get my readers to avoid. Changing the code to pass `$dispatch` skips a step. As I said: "Later, `$dispatch` will be passed to process() as well" [emphasis added]. Your getting ahead of the lesson. (Stop being a teacher's pet.) You're not passing the args directly to the appropriate sub. You're passing the arguments to every subroutine. Let me illustrate the point with a different example. `my $dispatch = { 1 => sub { return search_menu($current_user) }, 2 => sub { return edit_name($book) }, 3 => sub { return add_entry($book) }, 4 => sub { return delete_entry($book) }, 5 => sub { return save_default($current_user) }, 6 => \sub{ print "Goodbye!\n"; die; }, e => \sub{ print "Goodbye!\n"; die; }, }; &{ $dispatch->{ $choice } };` [download] Here, the arguments are defined in the dispatch table. I would like to help my readers think in broad terms instead of solving just this one problem. Your solution works fine, but more than 1400 people view these posts and most don't ask questions. My goal is to reach a wide audience with code examples and explanations that can be applied to other problems as well. It would seem I'm better at anwering questions than at asking them. Thank you for your reply. HTH, Charles K. Clarkson Clarkson Energy Homes, Inc.	[reply] [d/l] [select]

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Re: Re: Re: Re: passing arguments in a dispatch table
by CharlesClarkson (Curate) on Apr 29, 2002 at 06:06 UTC

I have two problems with this aproach

$dispatch is not passed to process, making it a global variable. Just what I'd like to get my readers to avoid. Changing the code to pass $dispatch skips a step. As I said: "Later, $dispatch will be passed to process() as well" [emphasis added]. Your getting ahead of the lesson. (Stop being a teacher's pet.)
You're not passing the args directly to the appropriate sub. You're passing the arguments to every subroutine. Let me illustrate the point with a different example.
```
my $dispatch = {
    1   => sub { return search_menu($current_user) },
    2   => sub { return edit_name($book) },
    3   => sub { return add_entry($book) },
    4   => sub { return delete_entry($book) },
    5   => sub { return save_default($current_user) },
    6   => \sub{ print "Goodbye!\n"; die; },
    e   => \sub{ print "Goodbye!\n"; die; },
};

&{ $dispatch->{ $choice } };
[download]
```
Here, the arguments are defined in the dispatch table. I would like to help my readers think in broad terms instead of solving just this one problem. Your solution works fine, but more than 1400 people view these posts and most don't ask questions. My goal is to reach a wide audience with code examples and explanations that can be applied to other problems as well.

It would seem I'm better at anwering questions than at asking them. Thank you for your reply.

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