如何修改Moose属性句柄？

Question

按照phaylon的回答"如何灵活地向Moose对象添加数据？" ,假设我有以下Moose属性:

has custom_fields => (
    traits     => [qw( Hash )],
    isa        => 'HashRef',
    builder    => '_build_custom_fields',
    handles    => {
        custom_field         => 'accessor',
        has_custom_field     => 'exists',
        custom_fields        => 'keys',
        has_custom_fields    => 'count',
        delete_custom_field  => 'delete',
    },
);

sub _build_custom_fields { {} }

现在,假设我想尝试读取(但不是写入)不存在的自定义字段时会呱呱叫.我被phaylon建议custom_field用一个环绕修饰语包裹.我已经around按照Moose文档中的各种示例尝试了修饰符,但无法确定如何修改句柄(而不仅仅是对象方法).

或者,是否有另一种方法来实现这个croak-if-try-to-read-unfxisting-key？

Answer 1

它们仍然只是穆斯生成的方法.你可以这样做:

around 'custom_field' => sub {
    my $orig  = shift;
    my $self  = shift;
    my $field = shift;

    confess "No $field" unless @_ or $self->has_custom_field($field);

    $self->$orig($field, @_);
};

(croak目前在方法修饰语中不是很有用.它只会指向内部的Moose代码.)

实际上,您不需要使用around此功能.使用before更简单:

before 'custom_field' => sub {
    my $self  = shift;
    my $field = shift;

    confess "No $field" unless @_ or $self->has_custom_field($field);
};