Perl array attribute inside an object

Question

Tried to write a perl module with OOP, but it can add an object to an array, when I use Dump method, it will output wrong data like this. Where is my error ?

Thanks

bless( {
                 '_name' => 'CUSIP',
                 '_validation_array' => [],
                 '_seq' => '1'
               }, 'Field' );

source code:

 package Field;

    sub new {
    my $class = shift;
    my $self = {
        _name => shift,
        _seq => shift,
        _validation_array => [ @_ ],
    };

    bless($self, $class);
    return $self;
};

sub pushValidation(){
    my $validation = shift;   
    push(@{$self->{_validation_array}}, $validation);     
};

sub dump(){
    foreach my $validation (@{$self->{_validation_array} })   {
        #print Dumper($validation);#will work, 
        print $validation->{name}; #error, Use of uninitialized value
    }
}        
    1;

This is the way I call this method :

my $validationObj = new Validation($validation->{name}, $validation->{seq});
$field->pushValidation($validationObj);

score 6 · Accepted Answer · 2013-09-04 03:41:34Z

6

I see several problems here, but the most serious one is here:

sub pushValidation() {
    my $validation = shift;   
    push(@{$self->{_validation_array}}, $validation);     
};

This function is expecting a $self argument, but isn't shifting it from the arguments. You need to add use strict; at the top of your Perl file. If it had been enabled, the issue would have been immediately obvious:

Global symbol "$self" requires explicit package name at <filename> line <line>.

Same thing goes for the dump() function. (By the way, dump is a bad method name, as there is an (obscure) Perl builtin function with the same name. But that's not a huge issue.)

edited Sep 4, 2013 at 3:41

answered Sep 4, 2013 at 3:36

user149341

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4 Comments

user595234 Over a year ago

correct, I put the 'use strict', I see this error. how to fix it ?

user149341 Over a year ago

You need to shift out $self as the first argument to the function - e.g, add my $self = shift; before the $validation argument. Alternatively, unpack both at one: my ($self, $validation) = @_;.

user595234 Over a year ago

I made this change, inside the dump, use print $validation->{name}; still get error, "Use of uninitialized value in print"

user149341 Over a year ago

As I believe someone else pointed out in a comment, some of your attribute references have leading underscores (e.g, $self->{_name}) and some don't ($self->{name}). Either one will work, but you need to be consistent.

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