why do I receive the errror - excel

Question

in my code, I have a function which verifies if a cell from an worksheet contains valid values, meaning:
1. it contains something.
2. the contained value is not SPACE, TAB or ENTER.
when i am just checking the function within a print (to print the value returned by the function for a single cell), apparently, everything works fine.
when I am integrating the "print of the result" into a while loop, for checking a range of cells, it received the error message: Can't call method "value" on an undefined value at D:\test.pl
here is my code:
use strict;
use Spreadsheet::ParseXLSX;
my $parser = Spreadsheet::ParseXLSX->new();
sub check_cell($) {
my ( $worksheet, $a, $b ) = #_;
if ( $worksheet->get_cell( $a, $b )
or not ord( $worksheet->get_cell( $a, $b )->value() ) ~~ [ 32, 9, 10 ] )
{
return 1;
} else {
return 0;
}
}
my $workbook = $parser->parse('D:\test.pl data.xlsx');
if ( !defined $workbook ) {
die $parser->error(), ".\n";
}
my $worksheet = $workbook->worksheet(0);
my $i = 8;
while ( &check_cell( $worksheet, $i, 0 ) ) {
print &check_cell( $worksheet, $i, 0 ), "\n";
$i++;
}
if I remove the while and index increment, everything works fine.
Can anyone tell me why the error occurs in 1st case?
Thank you.

Answer 1

When you compare two strings for equallity, you have to use eq, not ==
while( check_cell($worksheet, $i, 0) eq "correct cell" ) {
#...
};
Also, it's more natural to return 0 or 1 in your check_cell sub, so you haven't to test the result in while loop:
sub check_cell {
# return 1 if it's ok, else 0
}
while( check_cell($worksheet, $i, 0) ) {
#...
};
And the smartmatch operator ~~ has been marked as experimental since Perl 5.18.0

Answer 2

When $worksheet->get_cell($a, $b) doesn't return a defined value, you can't call ->value on the undefined value it returned. Don't you want to use and instead of or in the condition?

Answer 3

in this case, it worked modifying the condition:
instead of this:
if ( $worksheet->get_cell( $a, $b )
or not ord( $worksheet->get_cell( $a, $b )->value() ) ~~ [ 32, 9, 10 ] )
{
return 1;
}
I used:
if ( $worksheet -> get_cell($a, $b) ) {
if ( not ord($worksheet -> get_cell($a, $b) -> value()) ~~ [32, 9, 10] ){
return 1;
}
}
and the scrit exits without any error.
Thank you guys for your help.