Perl困境-分配和返回散列

在这行代码中:

my %myhash = $self->{properties};

%myhash是散列,而$self->{properties}是散列 . 因此,您实际上返回了一个具有一个键/值对的散列,其中键是对散列的引用,而值是未定义的。

如果确实要返回哈希,请执行以下操作:

my %myhash = %{$self->{properties}};

或者,返回哈希引用。这通常比返回散列更好,因为它不会生成原始散列的副本,因此随着散列变大,内存效率会更高。下面是它的外观:

sub getProperties {
    my $self = shift;
    return $self->{properties};
}

然后在你的调用代码中而不是这个:

my %properties = $properties->getProperties();
$somevalue = $properties{'somekey'};

执行以下操作:

# getProperties returns a reference, so assign to a scalar
# variable ($foo) rather than a hash (%foo)
my $properties = $properties->getProperties();

# Use -> notation to dereference the hash reference
$somevalue = $properties->{'somekey'};

不是 $self->{properties}

$ perl t4.pl
size -> 42

t4.pl公司

#!/usr/bin.perl
use strict;
use warnings;

use t4;

my $t4 = t4->new();
my %hash = $t4->getProperties();
for my $key (keys %hash) {
  print "$key -> $hash{$key}\n";
}

package t4;

sub new {
  my $class = shift;
  my $self = {};
  $self->{properties}{size} = 42;
  bless ($self, $class);
}

sub getProperties {
  my $self = shift;
  my %myhash = %{$self->{properties}};
  return %myhash;
}

1;