Re: Getting my head round hashes
David,
You don't have a response set at execute. You have
a reference to a responce set. You need to use DBI
methods to access the results. Try this...
$response-execute();
my $hash = {};
while (my $rows = $response-fetchrow_hashref){
$hash-{$rows-{task_ID}} = $rows;
}
$response-finish();
use Data::Dumper;
print Dumper $response;
--- Greenhalgh David [EMAIL PROTECTED]
wrote:
Hi all,
I have a script which mostly works, but when I get
to the part with
hashes, it stops. I'm obviously doing something very
basically wrong,
but I can't see what. (been staring at so long it
could be anything.) A
segment of the code is below:
#!/usr/local/perl -wT
use strict;
use CGI;
# Do some stuff to identify the value of $marker
which will be a number
# Do MySQL query to grab the data to be manipulated
my $dbh=connect(DBI:mysql:database, user,
password);
my $query=(SELECT task_ID, priority FROM task_list
WHERE priority
$marker);
my $reponse-prepare($query);
$response-execute;
# $ response should now contain a
# reference to a hash filled with task_ID, priority
pairs
# Dereference $response
my %hash=%($response);
$response-finish;
# Subtract 1 from each value in the hash
my ($key, $priority, %newhash);
foreach $key (keys(%hash)){
my $priority=$hash{$key}--;
%newhash=($key, $priority);
}
# Put the new $priority values into the MySQL table
$query=(UPDATE task_list SET priority=? WHERE
task_ID=?);
$response-prepare($query);
foreach $key (keys{%newhash}){
$priority=$newhash{$key};
$response-execute($priority, $key);
}
$response-finish;
# Test the result
print Content-Type: text/html\n\n;
$query=(SELECT task_ID, priority FROM task_list);
$response-prepare($query);
$response-execute;
while($key, $priority){
print Priority: $priority Task Ident:
$keybr\n\n;
}
Would someone be patient enough to point out the
mistake?
Thanks
Dave
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Re: Getting my head round hashes
Kristofer,
Thank you.
It was a big mistake to forget the method.
I think I still have problems with catching when to use $ or %. I don't
fully understand this section of the code:
my $hash = {};
while (my $rows = $response-fetchrow_hashref){
$hash-{$rows-{task_ID}} = $rows;
}
Why is hash declared as my $hash and not my %hash? and how does the
final line result in a hash?
I am sorry, these are basic questions but I haven't got the hang of the
logic yet.
Dave
On Thursday, June 5, 2003, at 07:25 pm, Kristofer Hoch wrote:
David,
You don't have a response set at execute. You have
a reference to a responce set. You need to use DBI
methods to access the results. Try this...
$response-execute();
my $hash = {};
while (my $rows = $response-fetchrow_hashref){
$hash-{$rows-{task_ID}} = $rows;
}
$response-finish();
use Data::Dumper;
print Dumper $response;
--- Greenhalgh David [EMAIL PROTECTED]
wrote:
Hi all,
I have a script which mostly works, but when I get
to the part with
hashes, it stops. I'm obviously doing something very
basically wrong,
but I can't see what. (been staring at so long it
could be anything.) A
segment of the code is below:
#!/usr/local/perl -wT
use strict;
use CGI;
# Do some stuff to identify the value of $marker
which will be a number
# Do MySQL query to grab the data to be manipulated
my $dbh=connect(DBI:mysql:database, user,
password);
my $query=(SELECT task_ID, priority FROM task_list
WHERE priority
$marker);
my $reponse-prepare($query);
$response-execute;
# $ response should now contain a
# reference to a hash filled with task_ID, priority
pairs
# Dereference $response
my %hash=%($response);
$response-finish;
# Subtract 1 from each value in the hash
my ($key, $priority, %newhash);
foreach $key (keys(%hash)){
my $priority=$hash{$key}--;
%newhash=($key, $priority);
}
# Put the new $priority values into the MySQL table
$query=(UPDATE task_list SET priority=? WHERE
task_ID=?);
$response-prepare($query);
foreach $key (keys{%newhash}){
$priority=$newhash{$key};
$response-execute($priority, $key);
}
$response-finish;
# Test the result
print Content-Type: text/html\n\n;
$query=(SELECT task_ID, priority FROM task_list);
$response-prepare($query);
$response-execute;
while($key, $priority){
print Priority: $priority Task Ident:
$keybr\n\n;
}
Would someone be patient enough to point out the
mistake?
Thanks
Dave
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RE: Getting my head round hashes
You're not pulling in the DBI functions, for one thing. Short example of
using the hashref function built into DBI is shown below.
#!/usr/local/perl -wT
use strict;
use CGI;
use DBI; # need this!
my $marker = 5; (or whatever number)
my $dbh=DBI-connect(DBI:mysql:database:localhost,user,password);
my $sth=$dbh-prepare(SELECT task_ID, priority FROM task_list WHERE
priority ?);
$sth-execute($marker);
while(my($hashref) = $response-fetchrow_hashref) {
$hashref-{priority}--; # decrement each priority by 1
}
$sth-finish;
$dbh-disconnect;
Scot R.
inSite
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Re: Getting my head round hashes
Thanks Scott,
So %hashref now has the modified list of priorities with the task_ID as
the key.
I think I'm beginning to get the hang of this...
I do have use DBI in the code (clipped it by accident when I extracted
the segment) but you are quite right about me missing the the
fetchrow_hashref method. D'Oh.
Dave
On Thursday, June 5, 2003, at 07:55 pm, Scot Robnett wrote:
Sorry, forgot to comment something...yeeesh
#!/usr/local/perl -wT
use strict;
use CGI;
use DBI; # need this!
my $marker = 5; # (or whatever number)
my $dbh=DBI-connect(DBI:mysql:database:localhost,user,password);
my $sth=$dbh-prepare(SELECT task_ID, priority FROM task_list WHERE
priority ?);
$sth-execute($marker);
while(my($hashref) = $response-fetchrow_hashref) {
$hashref-{priority}--; # decrement each priority by 1
}
$sth-finish;
$dbh-disconnect;
Scot R.
inSite
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Re: Getting my head round hashes
On Thursday, Jun 5, 2003, at 21:43 US/Pacific, Mark Young wrote:
[..]
One nice way to learn about hashes, arrays, scalars and references, is
to learn the perl debugger and just experiment.
There is a perl debugger tutorial in the perl documentation.
[..]
My Compliments!
cf perldoc perldebug
perldoc perldebtut
folks would also be wise to check out
perldoc Data::Dumper
since these will help the user sort out whether the problem
is with some piece of perl arcania, or is it really the more
complex problem of how their cgi code is working!
Folks should never be afraid to just write a little piece of
perl, whip it in the debugger, and see if it is doing what
must be done...
To help 'debug' the html side of the problem, one either
needs to have
a. their web-server set to full debug mode,
and tail the logfile
b. cut a simple mini-web-server that is in debug mode
c. run simple scripts to act like a web-server...
To help, I have a small /bin/sh script I use:
vladimir: 57:] sed 's/^/###/' ~/bin/test_cgi
!/bin/sh
###
###METHOD=$1
###SCRIPT=$2
###QUERY_STRING=$3
###DEBUG=$4
###
###REQUEST_METHOD=${METHOD}
###dir=`pwd`
###dir=`echo $dir | sed s'!.*\(/home\)!\1!'`
###SCRIPT_FILENAME=${dir}/$SCRIPT
###
###export REQUEST_METHOD SCRIPT_FILENAME QUERY_STRING
###
echo ${METHOD} ${SCRIPT} ${DEBUG}
###
###perl ${DEBUG} $SCRIPT
vladimir: 58:]
which I call with
test_cgi GET name_of_script query_string [ -d ]
say :
vladimir: 62:] test_cgi GET index.cgi callForm=bobfran=zoie
Content-Type: text/html
Content-Length: 487
!DOCTYPE HTML PUBLIC -//W3C//DTD HTML 4.01 Transitional//EN
htmlheadtitleHQ Admin Web Tool on vladimir/title/head
frameset border=0 cols=135,* frameborder=no framespacing=0
frameset border=0 rows=97,* frameborder=no framespacing=0
frame name=HqIcon scrolling=no src=html/icon.html
frame name=VertNav src=L1/L1_VertNav.cgi
/frameset
frame name=MainBody
src=L1/L1_MainBody.cgi?callForm=bobfran=zoie
/frameset/html
vladimir: 63:]
So that it 'acts' like a mini-web-server, the
'-d' option of course would take us into the perl debugger itself...
This will help get past the usual 'issues' with debugging
perl cgi scripts, that want to have one 'input' stuff
and type ^D or echo the query string in
Your mileage may vary
ciao
drieux
---
short shameful confession: It has been a long time since I
have actually used a command line debugger for things like 'c' code,
but fell into the need a while back, and myFascistHouseMate said,
'just use the gdb at the command line'
and I did and laughed,
hey, it's just like the perl debugger...
and my professional peers all began to cry and
move away from me on the Group W bench.
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RE: Getting my head round hashes
One nice way to learn about hashes, arrays, scalars and references, is
to learn the perl debugger and just experiment.
There is a perl debugger tutorial in the perl documentation.
You can print out the arrays and hashes w/o putting print statements
into your code, and that makes the experimentation very easy and
interesting.
Mark
-Original Message-
From: Greenhalgh David [mailto:[EMAIL PROTECTED]
Sent: Thursday, June 05, 2003 1:16 PM
To: [EMAIL PROTECTED]
Subject: Getting my head round hashes
Hi all,
I have a script which mostly works, but when I get to the part with
hashes, it stops. I'm obviously doing something very basically wrong,
but I can't see what. (been staring at so long it could be anything.)
A
segment of the code is below:
#!/usr/local/perl -wT
use strict;
use CGI;
# Do some stuff to identify the value of $marker which will be a
number
# Do MySQL query to grab the data to be manipulated
my $dbh=connect(DBI:mysql:database, user, password);
my $query=(SELECT task_ID, priority FROM task_list WHERE priority
$marker);
my $reponse-prepare($query);
$response-execute;
# $ response should now contain a
# reference to a hash filled with task_ID, priority pairs
# Dereference $response
my %hash=%($response);
$response-finish;
# Subtract 1 from each value in the hash
my ($key, $priority, %newhash);
foreach $key (keys(%hash)){
my $priority=$hash{$key}--;
%newhash=($key, $priority);
}
# Put the new $priority values into the MySQL table
$query=(UPDATE task_list SET priority=? WHERE task_ID=?);
$response-prepare($query);
foreach $key (keys{%newhash}){
$priority=$newhash{$key};
$response-execute($priority, $key);
}
$response-finish;
# Test the result
print Content-Type: text/html\n\n;
$query=(SELECT task_ID, priority FROM task_list);
$response-prepare($query);
$response-execute;
while($key, $priority){
print Priority: $priority Task Ident: $keybr\n\n;
}
Would someone be patient enough to point out the mistake?
Thanks
Dave
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