hashref and references

rightfield has asked for the wisdom of the Perl Monks concerning the following question:

Hi experts, I have one thing to finish this morning but my vpn is down and I can't get to my database. I wrote and tested the below piece of code last Friday and I didn't get the desired output. (I'm a Perl beginner BTW) The file was created and the correct number of lines were written to it. The output was not the key:value pairs I was trying to get from the MySQL database. Since I got the correct number of lines I am thinking I have a problem in my references in the foreach loop. Each line that did get written consisted of numbers 83208512 (I can't get to the network so I don't know how many) and there was one line for every record I expected.


my $query = "SELECT blah blah stuff to get";
my $sth = $dbh->prepare($query) or die "Can't prepare: $query. Reason:
+ $!";
$sth->execute($user_id)or die "Can't execute: $query. Reason: $!";

open( DATAOUT, ">$filename" );

while ( my $ref = $sth->fetchrow_hashref() ){
    foreach ( keys (%{$ref}) ) {
        print DATAOUT "$_"+":"+"$ref->{$_}\t";
    }
    print DATAOUT "\n";
};
[download]

Could you please take a moment and straighten me out with regards to my references. Thanks. rightfield P.S. - My vpn's been down over an hour now, so I don't think its coming back up soon that's why I asking for help instead of just banging at it until I get it right. Without a database at home I'm on hold. Maybe I'll spend my time installing MySQL and get a database at home.

Comment on hashref and references Download Code

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Re: hashref and references by kwaping (Priest) on May 22, 2006 at 15:22 UTC
Your use of references looks fine to me. I think this line contains the actual error: `print DATAOUT "$_"+":"+"$ref->{$_}\t";` [download] You're using Java syntax, not Perl. Try this instead: `print DATAOUT $_ . ":" . $ref->{$_} . "\t";` [download] Unless of course you really do want to add up the strings, instead of concatenate them! :) --- It's all fine and dandy until someone has to look at the code.	[reply] [d/l] [select]
Re: hashref and references by davorg (Chancellor) on May 22, 2006 at 15:23 UTC
`+` isn't the concatenation operator in Perl. You want `.` (a dot). Actually, here you just need to interpolate your values into your string. `print DATAOUT "$_:$ref->{$_}\t";` [download] -- <http://dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply] [d/l] [select]
Re: hashref and references by rightfield (Sexton) on May 22, 2006 at 15:47 UTC
Hello experts, I got my own answer: print DATAOUT "$_:$$ref{$_}\t"; That's the way the print should have been done. (My vpn is back up so I could try something similar I found in a book.) I hope you're there next time I really need help. Thanks, rightfield	[reply]