http://qs321.pair.com?node_id=11120051


in reply to oop, variable that counts the number of objects created

You can create a lexical variable in the class that gets incremented in the constructor and decremented in the destructor. A class closure method makes this value accessible from outside. Don't forget to call SUPER::new in child classes.

#!/usr/bin/perl use warnings; use strict; use feature qw{ say }; { package Car; my $count; sub new { my ($class, $name, $price) = @_; my $self = {name => $name, price => $price, speed => 0}; say 'Object car being created:'; say "Name: $name"; say "Price: $price\n"; ++$count; return bless $self, $class } sub speed_up { my ($self, $acc) = @_; return $self->{speed} += $acc } sub slow_down { my ($self, $acc) = @_; return $self->{speed} -= $acc } sub DESTROY { say 'Scrap!'; --$count } sub count { return $count } } { package Car::GeneralMotors::Firebird; use parent -norequire => 'Car'; sub new { my ($class, $price) = @_; $class->SUPER::new('General Motors Firebird', $price); } } my @cars; for (1 .. 10) { push @cars, 'Car'->new('Peel P50', 176_000); } splice @cars, 0, 5; say 'Car'->count; say 'It works for subclasses, too:'; my $f = 'Car::GeneralMotors::Firebird'->new(200_000); say 'Car'->count; undef $f; say 'Car'->count;

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

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Re^2: oop, variable that counts the number of objects created
by bliako (Prior) on Jul 30, 2020 at 09:55 UTC

    the only problem I see with this (and the other similar) is that it associates the count decrement with DESTROY which assumes "car-life" and "object-life" are the same but may not be.