Beefy Boxes and Bandwidth Generously Provided by pair Networks
Do you know where your variables are?
 
PerlMonks  

special $dbh can't error?

by themage (Friar)
on Oct 03, 2008 at 10:20 UTC ( #715176=perlquestion: print w/ replies, xml ) Need Help??
themage has asked for the wisdom of the Perl Monks concerning the following question:

(re)Blessed minds,

Imagine the following code:
use DBI; my $dbh=DBI->connect("dbi:mysql:hostname=localhost;database=somedb","u +serok","passwdok"); bless $dbh, "My::Special::DBI::db"; print "can error: ", $dbh->can("error"),"\n"; package My::Special::DBI::db; use base qw(DBI::db); sub error { my $dbh=shift; return $dbh->errstr(); }
I would expect that in this code, the $dbh->can("error") returned a reference to My::Special::DBI::db::error.

However, undef is returned.

Can anyone explain me what sets my expections out of sync with reality?

For extra-information, I tested this with:

perl -v This is perl, v5.8.7 built for x86_64-linux-gnu-thread-multi perl -v This is perl, v5.10.0 built for i486-linux-gnu-thread-multi
Thank you, everyone.

Comment on special $dbh can't error?
Select or Download Code
Re: special $dbh can't error?
by Anonymous Monk on Oct 03, 2008 at 10:43 UTC
    Can anyone explain me what sets my expections out of sync with reality?
    Probably because can isn't what you think it is. Try UNIVERSAL::can()
    use DBI; my $dbh=DBI->connect("dbi:SQLite:dbname=dbfile"); warn $dbh; print "can error: ", $dbh->can("error"),"\n"; print "UNIVERSAL::can((", UNIVERSAL::can($dbh,'error'),"\n"; eval {print $dbh->error('eeep');};warn $@ if $@; bless $dbh, "My::Special::DBI::db"; warn $dbh; print "can error: ", $dbh->can("error"),"\n"; print "UNIVERSAL::can((", UNIVERSAL::can($dbh,'error'),"\n"; eval {print $dbh->error('eeep');};warn $@ if $@; print "\n-----\n\n"; package My::Special::DBI::db; use base qw(DBI::db); sub error { my $dbh=shift; return $dbh->errstr(); } __END__ DBI::db=HASH(0x19b7f1c) at dbi.dbd.error.subclass.pl line 3. can error: UNIVERSAL::can(( Can't locate object method "error" via package "DBI::db" at dbi.dbd.er +ror.subclass.pl line 6. My::Special::DBI::db=HASH(0x19b7f1c) at dbi.dbd.error.subclass.pl line + 8. can error: UNIVERSAL::can((CODE(0x19978e4) -----
Re: special $dbh can't error?
by jethro (Monsignor) on Oct 03, 2008 at 12:30 UTC

    It seems 'can' is overriden by DBI and for it to know your method you would have to override it in turn.

Re: special $dbh can't error?
by massa (Hermit) on Oct 03, 2008 at 15:32 UTC
    base.pm seems to have a bug; if you use
    push @ISA, qw(DBI::db);
    instead of
    use base qw(DBI::db);
    the thing starts to work...
    []s, HTH, Massa (κς,πμ,πλ)

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://715176]
Approved by Corion
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others making s'mores by the fire in the courtyard of the Monastery: (7)
As of 2014-07-30 05:44 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    My favorite superfluous repetitious redundant duplicative phrase is:









    Results (229 votes), past polls