How to write a "caller-inspecting" module? - Perl

On Dec 13, 5:31 pm, kj <so...@987jk.com.invalid> wrote:
> Is it possible to write a module Foo such that if one wrote
>
> package Bar;
> use Foo;
>
> # rest of Bar defined here
>
> sub last_sub_in_Bar { do_something() }
>
> last_top_level_statement_in_Bar();
>
> # suitable moment!
>
> 1; # end of Bar
>
> then, at some *suitable moment* Foo would automatically inspect
> the Bar package (the "caller") and do something (e.g. add some
> methods to Bar) on the basis of this inspection. The "suitable
> moment" I'm referring to is right after last_sub_in_Bar has been
> defined and "last_top_level_statement_in_Bar();" has been executed.
>
> After playing around endlessly with CHECKs and INITs, I still have
> not come up with a solution to this problem. The closest to a
> solution I can come up with is to move the "use Foo" statement to
> right after last_top_level_statement_in_Bar().
>
> Is what I'm trying to do possible?
>

Carp's 'longmess' provides some stack introspection, eg,

package Foo;
use Carp;
my $trace = Carp::longmess;
...

$trace might then contain, eg,
at Bar.pm line 2
Bar::BEGIN() called at Foo.pm line 0
eval {...} called at Foo.pm line 0
require Bar.pm called at -e line 1
main::BEGIN() called at Foo.pm line 0
eval {...} called at Foo.pm line 0

You'd then have to pry 'Bar' from this 'mess'.
Kludgy and fragile though...so there may well
be a better way.

--
Charles DeRykus

In article <fjsmd4$3do$1@reader1.panix.com>, kj
<socyl@987jk.com.invalid> wrote:

> Is it possible to write a module Foo such that if one wrote
>
> package Bar;
> use Foo;
>
> # rest of Bar defined here
>
> sub last_sub_in_Bar { do_something() }
>
> last_top_level_statement_in_Bar();
>
> # suitable moment!
>
> 1; # end of Bar
>
> then, at some *suitable moment* Foo would automatically inspect
> the Bar package (the "caller")

Well, you can always use the caller() built-in to inspect the call
stack and decide what to do. You might also want to look at things such
as Hook::LexWrap for ideas.

If you need more help, give a concrete example about what you are doing
and what you are trying to accomplish.

Good luck,