with the hash below, I would like the clients array's reference :
my $this =
{
'name' => $name,
'max_clients' => $max_clients,
'clients' => ()
};
I can't do "\$this{'clients'};" to retrieve the reference.
You cannot store an array as a value in a hash table. You can only store a scalar value such as a reference to an array:
my $this =
{
'name' => $name,
'max_clients' => $max_clients,
'clients' => [],
};
See also perldoc perldsc.
Related
Not even sure if I used the right terminology..
This was the passed data.
$bug = bless({
'bug_id' => '25252',
'flag_types' => [
bless({
'name' => 'name1',
'flags' => [bless({
'id' => 488052,
}, 'Bugzilla::Flag')],
}, 'Bugzilla::FlagType'),
bless({
'name' => 'name2',
'flags' => [bless({
'id' => 488053,
}, 'Bugzilla::Flag')],
}, 'Bugzilla::FlagType'),
],
}, 'Bugzilla::Bug');
Why can I reference name with or without curly braces, but not the flags?
$_->flags gives error
Can't locate object method "flags"
my #isCrash = map {
print Dumper($_->name);
print Dumper($_->{name});
print Dumper($_->flags); # errors
print Dumper($_->{flags};
} #{ $bug->{flag_types} };
I get that flags is not a method, but why is it that I don't get such an error for name?
Your array contains objects of type Bugzilla::FlagType, they have a method name that "Returns the name of the flagtype".
I have a complex json data structure in perl like in the following example. I want to address an array element and store data.
Variable
$VAR1 = {
'dummy' => 'foo',
'profiles' => {
'Tags' => [
{
'###PLACEHOLDER###',
}
],
}
I can for example add an element at "###PLACEHOLDER###" but want later in the perl script to add beneath that Placeholder additional information.
Normally i would address these elements with $var->{profiles}->{Tags}->{PLACEHOLDER} but this is not working with an array.
I dont want to create everytime a foreach loop when i know the name exactly.
Any advice?
[UPDATE: used dpathr instead of dpath for the references to structures]
[UPDATE: used dpath instead of dpathr for the references to elements]
Data::DPath can do what you require. Here's code which returns a reference to any structure (hash or array) which contains an element whose value is ###PLACEHOLDER###:
use strict;
use warnings;
use Data::Dumper;
use Data::DPath qw[ dpath dpathr ];
my $struct = {
'dummy' => 'foo',
'profiles' => {
'ARRAY' => [ '###PLACEHOLDER###' ],
'HASH' => { key => '###PLACEHOLDER###' },
},
};
my $path = dpath( '//[value eq "###PLACEHOLDER###"]/..' );
my #matches = $path->match( $struct );
print Dumper \#matches;
It results in:
$VAR1 = [
[
'###PLACEHOLDER###'
],
{
'key' => '###PLACEHOLDER###'
}
];
If you want direct access to the element, change the path to
my $path = dpathr( '//*[value eq "###PLACEHOLDER###"]' );
with the result:
$VAR1 = [
\'###PLACEHOLDER###',
\'###PLACEHOLDER###'
];
It's not clear to me what you what "adding an element at ###PLACEHOLDER###" means. Elements can be added to arrays and hashes, and it's not clear to which array or hash you are referring.
To append an element to the array referenced by $var->{profiles}{Tags}, use
push #{ $var->{profiles}{Tags} }, $val;
This results in
$VAR1 = {
'dummy' => 'foo',
'profiles' => {
'Tags' => [
{
'###PLACEHOLDER###' => undef,
},
$val
],
}
To add an element to the hash referenced by the last element of the array referenced by $var->{profiles}{Tags}, use
$var->{profiles}{Tags}[-1]{$key} = $val;
This results in
$VAR1 = {
'dummy' => 'foo',
'profiles' => {
'Tags' => [
{
'###PLACEHOLDER###' => undef,
$key => $val,
},
],
}
Of course, if $key is ###PLACEHOLDER###, this results in
$VAR1 = {
'dummy' => 'foo',
'profiles' => {
'Tags' => [
{
'###PLACEHOLDER###' => $val,
},
],
}
In the below example, how would i print out the thread id?
$r_event = {
'type' => 'READ_' . $task . '_STARTED',
'timestamp' => $timestamp,
'threadid' => $threadId,
'fdn' => $fdn
};
You have a hash reference there (and those are often used as objects and that's what JSON calls an "object"). You can use the -> to dereference it and put the key you want in curlies:
print $r_event->{'threaded'};
This is just like a normal hash. Note the % and the parens instead of curlies:
%r_event = (
'type' => 'READ_' . $task . '_STARTED',
'timestamp' => $timestamp,
'threadid' => $threadId,
'fdn' => $fdn
);
In that case it's just $r_event{'threaded'} with no arrow since there's no reference.
My book Intermediate Perl covers this and you'll also find it in perlref.
Is there a way to update a value in a hash using a hash reference that points to the hash value?
My hash output looks like this:
'Alternate' => {
'free' => '27.52',
'primary' => 'false',
'used' => '0.01',
'name' => '/mydir/journal2',
'size' => '50.00'
},
'Primary' => {
'free' => '60.57',
'primary' => 'true',
'used' => '0.06',
'name' => '/mydir/journal',
'size' => '64.00'
}
};
I attempted to create a hash reference to the 'used' property in the hash and tried to update the value:
$hash_ref = \%hash->{"Primary"}->{used};
$hash_ref = "99%";
print $$hash_ref, "\n";
This changes the value of the hash, but I get the "Using a hash as a reference is deprecated at line X". I'd like to know if what I'm trying to do is possible and what I'm doing wrong.
...
'Primary' => {
'free' => '60.57',
'primary' => 'true',
'used' => '0.06',
'name' => '/mydir/journal',
'size' => '64.00'
}
...
Try to bypass the deprecation problem doing it like this:
...
my $hash_ref = $hash{'Primary'}; # if you declared `%hash = ( .. );`
# Or my $hash_ref = $hash->{'Primary'}; if you declared `$hash = { .. };`
print $hash_ref->{used}; # Prints 0.06
$hash_ref->{used} = '0.07'; # Update
print $href->{used}; # Prints 0.07
...
See perldsc, if you want to learn more.
Your failure started because you tried to create a hash reference to a scalar. That's kind of a meaningless goal as those are different data types. As Filippo already demonstrated, you already have hash references as values of your greater hash, so you can rely on that.
However, if you really want to create a reference to the scalar, you can just edit that value. This is how you'd do it:
use strict;
use warnings;
my $h = {
'Alternate' => {
'free' => '27.52',
'primary' => 'false',
'used' => '0.01',
'name' => '/mydir/journal2',
'size' => '50.00',
},
'Primary' => {
'free' => '60.57',
'primary' => 'true',
'used' => '0.06',
'name' => '/mydir/journal',
'size' => '64.00',
}
};
my $primary = $h->{Primary};
print $primary->{used}, "\n"; # Outputs 0.06
my $usedref = \$h->{Primary}{used};
$$usedref = '0.07';
print $primary->{used}, "\n"; # Outputs 0.07
I dumped a data structure:
print Dumper($bobo->{'issues'});
and got:
$VAR1 = {
'155' => {
'name' => 'Gender',
'url_name' => 'gender'
}
};
How can I extract 155?
How about if I have:
$VAR1 = {
'155' => {'name' => 'Gender', 'url_name' => 'gender'},
'11' => {'name' => 'Toddler', 'url_name' => 'toddler'},
'30' => {'name' => 'Lolo', 'url_name' => 'lolo'}
};
I want to print one key, i.e. the first or second to see the value of the key?
So, based on the example you posted, the hash looks like this:
$bobo = {
issues => {
155 => {
name => 'Gender',
url_name => 'gender',
},
},
};
'155' is a key in your example code. To extract a key, you would use keys.
my #keys = keys %{$bobo->{issues}};
But to get the value that 155 indexes, you could say:
my $val = $bobo->{issues}{155};
Then $val would contain a hashref that looks like this:
{
name => 'Gender',
url_name => 'gender'
}
Have a look at perldoc perlreftut.
It is a key in the hash referenced by $bobo->{'issues'}. So you would iterate through
keys %{$bobo->{'issues'}}
to find it.