Perl：使用 Moose 进行递归对象实例化

Question

在下面的示例代码中，我定义了一个 class Person 可以具有相同 class.

的子对象

当我调用 printTree 方法时，我期望得到以下输出

Sam    Ram    Geeta

我看到的是

SamRamRamRamRamRamRamRamRamRamRamR.....

关于我做错了什么以及如何实现我的目标的任何提示？

package Person;

use Moose;

has name => ( is => 'ro' );

my @kids;

sub addChild {
    my ( $self, $name ) = @_;
    my $k = Person->new( name => $name );
    push @kids, $k;
    return $k;
}

sub printTree {
    my $self = shift;
    print $self->name;
    $_->printTree foreach ( @kids );
}



no Moose;

package main;

my $s = Person->new( name => "Sam" );
my $r = $s->addChild( "Ram" );
my $g = $s->addChild( "Geeta" );

$s->printTree;

Answer 1

问题是 @Person::kids 不属于任何一个实例，你最终得到

@Person::kids = ($r, $g);
$s->printTree() loops through @Person::kids, calls
 $r->printTree() loops through @Person::kids, calls
  $r->printTree() loops through @Person::kids, calls
   $r->printTree() loops through @Person::kids, calls
    ...

您需要将其设为属性，例如

has kids => (
    isa => 'ArrayRef[Person]',
    traits => ['Array'],
    handles => {
        all_kids => 'elements',
        push_kids => 'push',
    },
    default => sub { [] },
);
sub addChild {
    my ($self, $name) = @_;
    my $k = Person->new(name => $name);
    $self->push_kids($k);
    return $k;
}
sub printTree {
    my ($self) = @_;
    print $self->name;
    $_->printTree foreach $self->all_kids;
}

您可以检查 perldoc Moose::Meta::Attribute::Native::Trait::Array 从 Array 特性中寻找其他有用的句柄。

Perl：使用 Moose 进行递归对象实例化

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