Re^4: Simple inheritance question

in reply to Re^3: Simple inheritance question
in thread Simple inheritance question

Yeah, $self->test will work (altho this still does not require a constructor for One, seems like a red herring):

#!/usr/bin/perl -w  
use strict;

{ package One;
  sub test {
    my $x = pop;
    print "$x\n";
  }
}

{ package Two;
  use base "One";
  sub new {
    my $self = {};
    bless($self);
  }
  sub eg {
    my $self = shift;
    $self->test(pop);
  }
}

my $obj = new Two();
$obj->eg("hello");
[download]

I guess this is starting to seem a little finnicky, but I would like to use test() as if it were a function internal to Two, not requiring an object.

Basically, I have two classes that share a bunch of such internal functions (no object required, it's just string parsing), so I thought the best thing would be to have a base class containing those.

In fact Exporter does work, see my reply to jethro.

Comment on Re^4: Simple inheritance question Download Code

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Re^5: Simple inheritance question by BrowserUk (Patriarch) on Apr 23, 2010 at 21:09 UTC
Basically, I have two classes that share a bunch of such internal functions (no object required, it's just string parsing) Put the functions into a third, non-class module, export them, and use it in both your class modules. Inheritance only works for methods, not plain ol' functions. And inheriting from a class that you've no intention of using inheritance--just so you can import some functions that live in the same file--leaves you open to all kinds of nasty surprises down the line. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. RIP an inspiration; A true Folk's Guy	[reply]
Re^5: Simple inheritance question by ikegami (Patriarch) on Apr 23, 2010 at 20:40 UTC
as if it were a function internal to Two, not requiring an object. As if it's something it isn't. So make it what you want it to be. `BEGIN { *Two::test = \&One::test; }` [download] It's really weird to export functions from a Class module, though.	[reply] [d/l]
Re^5: Simple inheritance question by webfiend (Vicar) on Apr 23, 2010 at 17:12 UTC
Glad you got the solution you needed. I was a little unclear on the original question. I also think it's interesting that `One` doesn't need a constructor in the object solution. It makes sense, considering that a One is never instantiated. I didn't realize that Perl's package handling let's you "inherit" from a package that isn't actually a class. We learn something every day if we give ourselves a chance.	[reply] [d/l]
Re^6: Simple inheritance question by chromatic (Archbishop) on Apr 23, 2010 at 19:36 UTC
I didn't realize that Perl's package handling let's you "inherit" from a package that isn't actually a class. There's no effective difference between a package and a class or a function and a method inside Perl 5. The internals don't care. If you treat something like a class name (by using it as an invocant), Perl 5 will use that package's namespace to find the destination method. Any reference blessed into a package will use that package's namespace to find its destination methods. Those packages don't even have to exist for Perl 5 to attempt to dispatch to them as invocants, but you will get dispatch errors if they don't.	[reply]

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