Hello William,
Thanks for the tip. In your example you did this:
threads->create(\&DerivedClass::doThat,$this);
And it seems to work. But if I am to make the 'DerivedClass' portion
dynamic (as it has to work with other subclasses eg DerivedClass2,
DerivedClass3), how can I do it?
I think it will have to be along the lines:
threads->create(\&$PackageName::doThat,$this);
Using a variable in place of the hard code. But I get get the syntax right.
By the way, how does one get the class (aka package) name from an object
instance?
[EMAIL PROTECTED] wrote:
In a message dated 3/28/2006 5:50:21 A.M. Eastern Standard Time,
[EMAIL PROTECTED] writes:
> Hi all,
>
> I have a need to do this (abstracted from the attached working code):
> package BaseClass;
> use threads;
>
> sub doThis
> {
> my $this = shift;
>
> threads->create(\&doThat,$this);
at this point, the compiler is looking for a subroutine doThat in
the package
BaseClass and all classes (i.e., packages) that BaseClass derives from.
however, BaseClass derives from nothing; in particular, it does not derive
from DerivedClass, where a subroutine named doThat (or more
specifically,
&DerivedClass::doThat) is defined. this is what the error message is
saying.
a way around the problem is to say
threads->create(\&DerivedClass::doThat,$this);
> }
>
> package DerivedClass;
> use base 'BaseClass';
>
> sub new
> {
> my $class = shift;
> my $this = $class->SUPER::new;
> return bless $this,$class;
> }
>
> sub doThat
> {
> ...
> }
>
> --- in an app that uses these objects ---
> use DerivedClass;
> my $o = DerivedClass->new;
> $o->doThis;
>
> The error is:
> Undefined subroutine &BaseClass::doThat called at BaseClass.pm
>
> Notice that doThat() is not in the base class, but rather in the
> subclass. Apparently Perl is not able to determine which package to use
> for doThat() within doThis(). I have tried:
perl knows exactly which package (or packages) to use because you have
told it exactly which to use.
>
> threads->create(\&{$this::doThat},$this);
>
> and a few other permutations, but they are all wrong. I'm quite sure
> it's matter of syntax.
>
> I will try to explain myself again if you are confused.
>
> Please advise. Thanks.
hi ji-haw --
consider the following:
-------- begin code ----------------
# t_jhfoo1.pl derived classes
28mar06waw
use strict;
use warnings;
package Foo;
sub foo {
bar();
}
sub bar{
Bar::drunk();
printf qq(i am bar in %s \n), __PACKAGE__;
}
package Bar;
use base 'Foo';
sub drunk {
printf qq(i am drunk in %s \n), __PACKAGE__;
}
package main;
Bar->foo(); # ok: &foo() defined in Bar or in one of its base classes
Foo::foo();
# Bar::foo(); # fails: no &Bar::foo() defined in package Bar
# drunk(); # fails: no &drunk() defined in package main
package Bar;
drunk; # ok
############################
package BaseClass;
use threads;
sub doThis
{
my $this = shift;
# threads->create(\&doThat,$this); # no
# threads->create(\&DerivedClass::doThat,$this); # should work
$this->{_code}->('YES');
}
sub new ($)
{
my ($class) = @_;
my %hash = (
_status=>'STOPPED',
_code => \&DerivedClass::doThat,
);
return bless \%hash,$class;
}
package DerivedClass;
use base 'BaseClass';
sub new
{
my $class = shift;
my $this = $class->SUPER::new;
return bless $this,$class;
}
sub doThat
{
my ($message) = @_;
print "in doThat: $message \n";
}
# --- in an app that uses these objects ---
package main;
# use DerivedClass;
my $o = DerivedClass->new;
$o->doThis;
------------ end code ----------------
hth -- bill walters
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