Pointer to a Hash

[redd99]

What is the difference between setting a hash like this:

$fooref->bar('cat');

and like this:

$fooref->{bar} = 'dog';

Apparently each statement is setting an entirely different hash.
Which is the proper way to do it?

And also if I were to concatenate the hash with a string using double quotes how would i do it?

I tried:

print "This is a $foo->bar";

But perl does not interpret the "->" symbol.

I tried this:

print "This is a $$foo{bar}";

which works but how do I get perl to interpret the "->" symbol?

use Class::Struct;

struct foo =>
{
  bar => '$'
};

my $fooref = foo->new();

$fooref->bar('cat');
$fooref->{bar} = 'dog';

print $fooref->bar;
print "\n";
print $fooref->{bar};

 

[Kirsle]

The format "$fooref->bar('cat')" isn't a hashref. Instead, $fooref is a reference to an object named foo, which has a subroutine named "bar", and presumably it lets you get/set the value of an internal private hashref by using the subroutine interface.

It's like this:

package foo;

sub new {
   return bless {}, "foo";
}

sub bar {
   my ($self,$value) = @_;
   if (defined $value) {
      $self->{bar} = $value;
   }
   return $self->{bar};
}

package main;

my $fooref = new foo();
$fooref->bar("cat");
print $fooref->bar();

The format "$fooref->{bar}" is a proper hash reference like normal.

So the first one is a subroutine, which hides a data structure behind it, the second is a data structure.

As for the arrow syntax: you can't call subroutines/methods on an object inside quotes, but you can get values out of a hashref.

# method call:
print "the value is ", $fooref->bar(), ".\n";
# hashref fetch:
print "the value is $fooref->{bar}.\n";

Perl recognizes the -> in your variables as long as everything is valid, i.e. the arrow only works to get members out of a referenced data structure. You can't call methods inside of quotes by using arrows, though.

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