perl pass object method reference as parameter to function

Question

i'm trying to do something like this:

-- source file 1

my $queue = Thread::Queue->new();
MyModules::populateQueue(<pass $queue->enqueue method reference);
...

-- package file

package MyModules

sub populateQueue {
  my $enqueue = $_[0];
  my $item = <find item to add to queue>;
  $enqueue->($item);

...

first, i'm not able to add "bless" to Thread::Queue

i've tried a couple of suggestions i found in stackoverflow:

my $enqueueRef = $queue->can('enqueue');
MyModules::populateQueue(\&enqueueRef); <--- fails in the package at line

$enqueue->($item) with undefined subroutine

MyModules::populateQueue(\&queue->enqueue) <-- same failure as above

any idea how to pass a method of an object as a parameter to a function that can then be used in the function?

just wrap it around sub: sub { $queue->enqueue; }

Miguel Prz
– Miguel Prz

2017-11-02 14:52:06 +00:00
Commented Nov 2, 2017 at 14:52 — Miguel Prz
– Miguel Prz, Commented Nov 2, 2017 at 14:52
There's also the curry module on CPAN.

simbabque
– simbabque

2017-11-02 15:06:45 +00:00
Commented Nov 2, 2017 at 15:06 — simbabque
– simbabque, Commented Nov 2, 2017 at 15:06

amon · Accepted Answer · 2017-11-02 15:10:32Z

8

Perl doesn't have a concept of a bound method reference. my $enqueue = $object->can('method') will return a code ref to a method if it exists, but the code ref isn't bound to that particular object – you still need to pass it as the first argument ($queue->$enqueue($item) or $enqueue->($queue, $item)).

To pass a bound method, the correct solution is to use an anonymous sub that wraps the method call:

populate_queue(sub { $queue->enqueue(@_) });

answered Nov 2, 2017 at 15:10

amon

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1 Comment

schleprock Over a year ago

just to add clarity, i did the following in the MyModules package: MyModules::populateQueue(sub {$queue->enqueue(@_)}); which works.

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