How to access data stored in Hash

Question

I have this code:

$coder = JSON::XS->new->utf8->pretty->allow_nonref;
%perl = $coder->decode ($json);

When I write print %perl variable it says HASH(0x9e04db0). How can I access data in this HASH?

Solution 1

The return value of decode isn't a hash and you shouldn't be assigning it to a %hash -- when you do, you destroy its value. It's a hash reference and should be assigned to a scalar. Read perlreftut.

Solution 2

As the decode method actually returns a reference to hash, the proper way to assign would be:

%perl = %{ $coder->decode ($json) };

That said, to get the data from the hash, you can use the each builtin or loop over its keys and retrieve the values by subscripting.

while (my ($key, $value) = each %perl) {
    print "$key = $value\n";
}

for my $key (keys %perl) {
    print "$key = $perl{$key}\n";
} 

Solution 3

JSON::XS->decode returns a reference to an array or a hash. To do what you are trying to do you would have to do this:

$coder = JSON::XS->new->utf8->pretty->allow_nonref;
$perl = $coder->decode ($json);

print %{$perl};

In other words, you'll have to dereference the hash when using it.

Comments

[Jay Gridley]

OK, I figured out that print keys %{$perl} gets me key from Hash, but print values %{$perl} gets me another Hash reference. So I stored this reference in new scalar variable, but when I try to access data in this Hash, it gives me nothing. $json = '{"glossary": {"title": "example glossary","GlossDiv": {"title": "S"}}}'; $coder = JSON::XS->new->utf8->pretty->allow_nonref; $perl = $coder->decode ($json); print keys %{$perl},"\n"; #give me glossary print values %{$perl},"\n"; #give me HASH(address) my $val = values %{$perl}; # store address print keys %{$val}; ##give nothing -- title expected