How do I store a 2d array in a hash in Perl?

Question

I am struggling through objects in perl, and am trying to create a 2d array and store it in a hash field of my object. I understand that to create a 2d array I need an array of references to arrays, but when I try to do it I get this error: Type of arg 1 to push must be array (not hash element) The constructor works fine, and set_seqs works fine, but my create_matrix sub is throwing these errors.

Here is what I am doing:

sub new {
    my ($class) = @_;
    my $self = {};
    $self->{seq1} = undef;
    $self->{seq2} = undef;
    $self->{matrix} = ();
    bless($self, $class);
    return $self;
}
sub set_seqs {
    my $self = shift;
    $self->{seq1} = shift;
    $self->{seq2} = shift;
    print $self->{seq1};
}

sub create_matrix {
    my $self = shift;
    $self->set_seqs(shift, shift);
    #create the 2d array of scores
    #to create a matrix:
    #create a 2d array of length [lengthofseq1][lengthofseq2]
    for (my $i = 0; $i < length($self->{seq1}) - 1; $i++) {
        #push a new array reference onto the matrix
        #this line generates the error
        push(@$self->{matrix}, []);
    }
}

Any idea of what I am doing wrong?

Answer 1

You're missing an extra set of braces when you dereference $self. Try push @{$self->{matrix}}, [].

When in doubt (if you're not sure if you're referring to the correct value in a complicated data structure), add more braces. :) See perldoc perlreftut.