Perl, get all hash values

Question

Let's say in Perl I have a list of hash links, and each one should contain a specific field, say foo . I want to create a list containing all foo mappings. 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 to do this in Perl?

Answer 1

Yes. there is.

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

Answer 2

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 the entire element of the second argument.

grep also cool filters the items in the list and works the same way.

Answer 3

Evan's answer is close, but will return hashrefs, not foo.

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

Answer 4

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