How do I call a function name that is stored in a hash in Perl?
- by Ether
I'm sure this is covered in the documentation somewhere but I have been unable to find it... I'm looking for the syntactic sugar that will make it possible to call a method on a class whose name is stored in a hash (as opposed to a simple scalar):
use strict; use warnings;
package Foo;
sub foo { print "in foo()\n" }
package main;
my %hash = (func => 'foo');
Foo->$hash{func};
If I copy $hash{func} into a scalar variable first, then I can call Foo->$func just fine... but what is missing to enable Foo->$hash{func} to work?
(EDIT: I don't mean to do anything special by calling a method on class Foo -- this could just as easily be a blessed object (and in my actual code it is); it was just easier to write up a self-contained example using a class method.)
EDIT 2: Just for completeness re the comments below, this is what I'm actually doing (this is in a library of Moose attribute sugar, created with Moose::Exporter):
# adds an accessor to a sibling module
sub foreignTable
{
my ($meta, $table, %args) = @_;
my $class = 'MyApp::Dir1::Dir2::' . $table;
my $dbAccessor = lcfirst $table;
eval "require $class" or do { die "Can't load $class: $@" };
$meta->add_attribute(
$table,
is => 'ro',
isa => $class,
init_arg => undef, # don't allow in constructor
lazy => 1,
predicate => 'has_' . $table,
default => sub {
my $this = shift;
$this->debug("in builder for $class");
### here's the line that uses a hash value as the method name
my @args = ($args{primaryKey} => $this->${\$args{primaryKey}});
push @args, ( _dbObject => $this->_dbObject->$dbAccessor )
if $args{fkRelationshipExists};
$this->debug("passing these values to $class -> new: @args");
$class->new(@args);
},
);
}
I've replaced the marked line above with this:
my $pk_accessor = $this->meta->find_attribute_by_name($args{primaryKey})->get_read_method_ref;
my @args = ($args{primaryKey} => $this->$pk_accessor);
PS. I've just noticed that this same technique (using the Moose meta class to look up the coderef rather than assuming its naming convention) cannot also be used for predicates, as Class::MOP::Attribute does not have a similar get_predicate_method_ref accessor. :(
