如何在子例程中取消引用哈希?如何像在调用例程中那样对其进行处理

Question

我有一个perl例程，它从.csv文件中生成散列。应该在子例程中检查值。

所以我有一个散列%my_values，并调用子程序check (%my_values):

sub read_csv {
...
# key:   headline entry
# value: the value in the current row
%my_hash;
...
my ($has_error, $err_msg) = check (%my_hash);
}
sub check {
my($hash_ref) = @_;
%my_hash = %$hash_ref;
# Get the artikel number of the article
$my_hash {'article_number'} = get_artnr($my_hash {'article'});
if (not $my_hash{'article_number'}) {
return 1, "Article $my_hash{'article'} not found!";
}
# check price (I'm in germany, there must be a conversation from ',' to '.')
$my_hash {'price'} =~ s/,/./;
if (not $my_hash{'price'} =~ m/^d+(.d+)?$/) {
return 1, "Invalid format of price";
}
return 0, "";
}

起初，这似乎很有效。但后来我意识到，价格格式和密钥article_number都不可用。

直接在参考文献上工作使其成为：

# In this case, it works!
sub check {
my($hash_ref) = @_;
# Get the artikel number of the article
$hash_ref->{'article_number'} = get_artnr($hash_ref->{'article'});
if (not $hash_ref->{'article_number'}) {
return 1, "Article $hash_ref->{'article'} not found!";
}
# check price (I'm in germany, there must be a conversation from ',' to '.')
$hash_ref->{'price'} =~ s/,/./;
if (not $hash_ref->{'price'} =~ m/^d+(.d+)?$/) {
return 1, "Invalid format of price";
}
return 0, "";
}

所以我认为%my_hash = %$hash_ref;会复制引用，而不是取消引用。

如何在子例程中取消引用哈希？如何像在调用例程中那样对其进行处理？

Answer 1

下面是一个使用Perl 5.22中引入的名为refaliasing的新功能的示例(可选地与5.26中引入的declard_refs功能组合(

use v5.26;
use warnings;  # IMPORTANT: this line must come before "use experimental"
use strict;
use feature qw(say); 
use experimental qw(declared_refs refaliasing);
{  # <-- introduce scope to avoid leaking lexical variables into subs below
my %hash = (a=>1, b=>2);
check(%hash);
say "Value of 'a' key is now: ", $hash{a};
}
sub check {
my (%hash) = @_;
$hash{a} = 3;
}

输出：

Value of 'a' key is now: 3

或者，您可以使用箭头操作符：

sub check {
my ($hash) = @_;
$hash->{a} = 3;
}