Exporting variables from a hash

[pmak]

Let's say I have this:

my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);

What could I put for magic_function() such that it'll have this effect,
based on the keys and values of the hash passed to it:
my $id = 'pmak';
my $name = 'Philip Mak';
my $level = 50;

 

[Gunnar Hjalmarsson]

Let's say I have this:

my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);

What could I put for magic_function() such that it'll have this
effect, based on the keys and values of the hash passed to it:
my $id = 'pmak';
my $name = 'Philip Mak';
my $level = 50;

sub magic_function {
my $href = shift;
my $id = $href->{id};
my $name = $href->{name};
my $level = $href->{level};

# do stuff now
}

 

[Anno Siegel]

Let's say I have this:

my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);

What could I put for magic_function() such that it'll have this effect,
based on the keys and values of the hash passed to it:
my $id = 'pmak';
my $name = 'Philip Mak';
my $level = 50;

No way.

A sub cannot declare lexical variables in the scope of its call.

Simply use the hash and access "$data{ id}" instead of "$id", etc.

If that is inconvenient, what you can do is

my ( $id, $name, $level) = @data{ qw( id name level)};

but that's neither magic nor a sub. In particular, it doesn't try
to extract the names of program variables from the data in the hash.
The latter is impossible with lexicals and inadvisable with package
variables.

Anno

 

[Brian McCauley]

Let's say I have this:

my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);

What could I put for magic_function() such that it'll have this effect,
based on the keys and values of the hash passed to it:
my $id = 'pmak';
my $name = 'Philip Mak';
my $level = 50;

You would have to use a source filter.

But do _not_ do it.

 

[Peter Scott]

Let's say I have this:

my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);

What could I put for magic_function() such that it'll have this effect,
based on the keys and values of the hash passed to it:
my $id = 'pmak';
my $name = 'Philip Mak';
my $level = 50;

Just to show how unwise this is, here's what it would take to
literally satisfy your request:

sub magic_function {
use Filter::Simple sub {
s/^\s*magic_function\s*\(\s*\\\s*%(\w+).*?;/my \$id = \$$1\{id\};/mg
};
BEGIN { import() }
}
my %data = (id => 'pmak', name => 'Philip Mak', level => 50);
magic_function(\%data);
print "id = $id\n";

Extension to handle the other variables is left as an exercise
for the reader. It also requires that all the keys be
explicitly named. But this is sick; don't do it.

Why would you ask for this in the first place? If you're
going to write code containing $id, for example, why not write
$data{id}, or, if you're going to repeatedly refer to that
and want to save space, write my $id = $data{id} and then go
on to use $id?

More importantly, why would you want to create something that
has unpredictable side effects, so that if one day a new key
gets added to the hash that happens to match a variable you're
already using, your program will fail in some bizarre way?

If the equivalent of %data in the real code is a long
expression you don't want to type repeatedly, then just make
a reference to it:

my $hr = \%blahblahblah...
... $hr->{id} ...

When you see a variable in your program you want to have a
fighting chance of figuring out where it came from.