哈希的代理对象？

Proxy object for a hash?

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：

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#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;

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

一个可能的解决方案(基于 How to add subscripts to my custom Class in Perl 6?)是将 Associative 的实现委托给内部散列，但覆盖 AT-KEY 方法以将默认 Scalar 替换为Proxy:

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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}