object - 哈希的代理对象？

Question

如何为哈希创建代理对象？我似乎找不到传递哈希键的方法:

#sub attr() is rw {
sub attr($name) is rw {
  my %hash;
  Proxy.new(
    FETCH => method (Str $name) { %hash«$name» },
    STORE => method (Str $name, $value) { %hash«$name» = $value }
  );
}

my $attr := attr();
$attr.bar = 'baz';
say $attr.bar;

Answer 1

一个 Proxy是单个容器 aka Scalar 的替代品.一个 Hash是复数容器，其中每个元素默认为 Scalar .

一种可能的解决方案(基于 How to add subscripts to my custom Class in Perl 6? )是委托(delegate) Associative 的实现到内部散列但覆盖 AT-KEY替换默认Scalar的方法与 Proxy :

class ProxyHash does Associative {

  has %!hash handles
    <EXISTS-KEY DELETE-KEY push iterator list kv keys values gist Str>;

  multi method AT-KEY ($key) is rw {
    my $element := %!hash{$key};
    Proxy.new:
      FETCH => method ()       { $element },
      STORE => method ($value) { $element = $value }
  }
}

my %hash is ProxyHash;
%hash<foo> = 42;
say %hash; # {foo => 42}