Using Objects across files and packages

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

Hi all,
I am just getting into using Perl objects. When I want to use my objects across files (and packages), the only way I have found to do so is to pass the reference to the object:

# File1

use ObjectMaker; # ObjectMaker has all the exporter stuff
use Foo;

my $Object = ObjectMaker->new();

&Foo::DoSomething(foo, bar, \$Object);
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But I thought new() returned a reference? So the way I have been accessing my objects in the other files is

# File 2

package Foo;

use ObjectMaker;

sub DoSomething
{
   my $foo = shift;
   my $bar = shift;
   my $Object = shift;

   ...
   my $blub = $$Object->MethodName(blah);
}

1;
[download]

Is there a more accepted way of doing this or am I on the right track?

Thanks for any enlightment from this august body,

Bob C.

Comment on Using Objects across files and packages Select or Download Code

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Re: Using Objects across files and packages by itub (Priest) on May 06, 2004 at 21:46 UTC
Indeed, object constructors return a reference. In general, you should just use that reference without further indirection. `my $Object = ObjectMaker->new(); Foo::DoSomething(foo, bar, $Object); $Object->MethodName(blah);` [download] You only need to do `Foo::DoSomething(foo, bar, \$Object);` in the very uncommon case where you want `DoSomething` to be able to change where your reference (`$Object`) points to. Updated to be add more details: for example, `DoSomething(foo, bar, \$Object); print $Object; # prints "42" sub DoSomething { my $foo = shift; my $bar = shift; my $Object = shift; $$Object = 42; }` [download] Now the caller will notice that his $Object is not longer an object reference but a scalar with value 42! This way of passing parameters by reference so that they can be modified is very common in C and Fortran, but not so common in Perl	[reply] [d/l] [select]
Re: Using Objects across files and packages by NetWallah (Canon) on May 06, 2004 at 21:59 UTC
I think the confusion is in the interpretation of this line: `my $blub = $$Object->MethodName(blah);` [download] The -> operator already does a dereference. The extra "$" would cause a double-dereference, so it should not be used. Offense, like beauty, is in the eye of the beholder, and a fantasy. By guaranteeing freedom of expression, the First Amendment also guarntees offense.	[reply] [d/l]