[英]Perl Hash by reference
so I'm trying to write a subroutine that takes a hash parameter and adds a couple key-value pairs to it (by reference). 所以我正在尝试编写一个子程序,它接受一个哈希参数,并为它添加几个键值对(通过引用)。 So far, I've got this:
到目前为止,我有这个:
addParams(\%params);
sub addParams
{
my(%params) = %{$_[0]}; #First argument (as a hash)
$params{"test"} = "testing";
}
But for some reason, It doesn't seem to add the 'test' key. 但出于某种原因,它似乎没有添加“测试”键。 I am new to Perl, but isn't this how you pass a hash by reference?
我是Perl的新手,但这不是你通过引用传递哈希的方式吗? Thanks beforehand.
先谢谢。
You can use the hash-ref without de-referencing it: 您可以使用hash-ref而无需取消引用它:
addParams(\%params);
sub addParams
{
my $params = shift;
$params->{"test"} = "testing";
}
EDIT: 编辑:
To address your code's issue, when you do: 要解决代码问题,请执行以下操作:
my(%params) = %{$_[0]};
You're actually making a copy of what the ref points to with %{...}. 你实际上正在复制ref指向%{...}的内容。 You can see this via a broken down example (no function, same functionality):
你可以通过一个细分的例子看到这个(没有功能,相同的功能):
my %hash = ( "foo" => "foo" );
my %copy = %{ \%hash };
$hash{"bar"} = "bar";
$copy{"baz"} = "baz";
print Dumper( \%hash );
print Dumper( \%copy );
Run: 跑:
$ ./test.pl
$VAR1 = {
'bar' => 'bar',
'foo' => 'foo'
};
$VAR1 = {
'baz' => 'baz',
'foo' => 'foo'
};
Both hashes have the original 'foo => foo', but now each have their different bar/baz's. 两个哈希都有原始的'foo => foo',但现在每个哈希都有不同的bar / baz。
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