What is the proper syntax for storing an array into a Perl hash?

Question

I'm creating a new object like this:

TestObject->new(@array1, @array2)

My new method looks like this:

sub new {
  my $class = shift;
  my $self = {};

  my $self->{Array1} = shift;
  my $self->{Array2} = shift;

  bless($self, $class);

  return $self;
}

As a simple test to access the data, I'm trying this, and then once I get it working, I can build more meaningful logic:

sub mymethod {
  my $self = shift;
  my $param = shift;

  my $array1Value = shift(my $self->{Array1});
  my $array2Value = shift(my $self->{Array2});

  print $array1Value." ".$array2Value;
}

But when I call mymethod, I get this error:

Type of arg 1 to shift must be array (not hash element) at Tests/MyObject.pm line 21, near "})"

Suggestions? I read this page on Perl data structures, but they don't have examples for creating a hash of arrays using arguments to a method using shift. So my problem might be there.

Answer 1

When you pass arrays as parameters, they are flattened. You can pass references to them. See perlsub

#!/usr/bin/env perl

package foo;

sub new {
    my $class = shift;
    my $self = {};

    $self->{Array1} = shift;
    $self->{Array2} = shift;

    bless($self, $class);

    return $self;
}

sub mymethod {
  my $self = shift;
  my $param = shift;

  my $array1Value = shift( @{$self->{Array1}} );
  my $array2Value = shift( @{$self->{Array2}} );

  print "$array1Value $array2Value\n";
}

package main;

my @a = ( 0, 1, 2);
my @b = ( 3, 4, 5);
my $o = new foo( \@a, \@b );;
$o->mymethod;

Answer 2

you need to derefernece the array ref:

@{$self->{Array2}}

By the way if you are using OO I emphatically suggest you look into Moose. It will make your life much easier!

Answer 3

you have to use pointers to arrays, not arrays in this case:

  TestObject->new([@array1], [@array2])

and then later

my $array1Value = shift(@{$self->{Array1}});

Answer 4

You're shifting an arrayref instead of an actual array.

The syntax ytou're probably looking for is:

my $array1Value = shift @{ $self->{Array1} };
my $array2Value = shift @{ $self->{Array2} };

Note how the array is dereferenced using @.