Perl, get all hash values

Question

Let's say in Perl I have a list of hash references, and each is required to contain a certain field, let's say foo . I want to create a list that contains all the mappings of foo . If there is a hash that does not contain foo the process should fail.

@hash_list = (
 {foo=>1},
 {foo=>2}
);

my @list = ();
foreach my $item (@hash_list) {
   push(@list,$item->{foo});
}

#list should be (1,2);

Is there a more concise way of doing this in Perl?

Answer 1

Yes. there is.

my @list = map {
    exists $_->{foo} ? $_->{foo} : die 'hashed lacked foo'
  }
  @hash_list
;

Answer 2

Evan 的回答很接近，但会返回 hashrefs 而不是 foo 的值。

my @list = map $_->{foo} grep { exists $_->{foo} } @hash_list

Answer 3

You can use the map function for this :

@hash_list = (
 {foo=>1},
 {foo=>2}
);

@list = map($_->{foo}, @hash_list);

map applies the function in the first argument over all element of the second argument.

grep is also cool to filter elements in a list and works the same way.

Answer 4

if ( @hash_list != grep { exists $_->{foo} } @hash_list ) {
    # test failed
}

Answer 5

TLDR Answer

If you want to get the values of a hash, use the values() function. Like this...

print Dumper(values %$hash);

Source

values HASH

In list context, returns a list consisting of all the values of the named hash.

(Source: PerlDoc.org. )

Demo

Working Demo Online at: IDEOne

use Data::Dumper;

my $hash = {
    soybeans=>1,
    chickpeas=>2,
};

print Dumper(values %$hash);