dynamic methods with variables

jorg has asked for the wisdom of the Perl Monks concerning the following question:

Hi all,
This post describes how one can achieve dynamic method calling using scalars.

my $foo = Obj->new;
for (qw( create init add )) {
  $foo->$_();  # note -- $foo->$_ will not work, ()'s needed
}
[download]

This approach works fine as long as you're not passing parameters along.
I want to do something along the lines of :

my $method = 'Quantize';
my $parameters = qw (colorspace=>'gray' compression=>'none');
my $image = Image::Magick->new;
$image->Read('/share/colortransition.jpg');
$image->${method}($parameters);
$image->write(filename=>'/share/graytransition.jpg');
[download]

... but i'm getting Argument "colorspace=>'gray'" isn't numeric in subroutine entry at im.pl line 10.Now this tells me that probably the parameter passing works but it's expecting a numeric parameter and the "qw" garbles it somehow. Is my observation correct?

Jorg

"Do or do not, there is no try" -- Yoda

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Re: dynamic methods with variables by liz (Monsignor) on Jul 30, 2003 at 12:47 UTC
You're mixing metaphors ;-) Try: `my $parameters = {colorspace=>'gray', compression=>'none'};` [download] Seems you're mixing up qw() with the anonymous hash reference constructor {}. Liz	[reply] [d/l]
Re: dynamic methods with variables by broquaint (Abbot) on Jul 30, 2003 at 12:48 UTC
You need to drop the `qw()` and change `$parameters` to an array e.g `my @parameters = (colorspace = >'gray', compression = >'none');` [download] Because as it stood `$parameters` was being assigned `compression=>'none'` as your code really looked like this `my $parameters = (q[colorspace=>'gray'], q[compression=>'none']);` [download] See. `perlop` for more info on the workings of `qw()`. HTH `_________ broquaint`	[reply] [d/l] [select]
Re: dynamic methods with variables by jorg (Friar) on Jul 30, 2003 at 13:11 UTC
dow ... I could've stared at this for ages without spotting it .. Thanks! Jorg "Do or do not, there is no try" -- Yoda	[reply]