note
tobyink
<p>Perl attributes are typically handled at CHECK time - between compile time (BEGIN) and INIT time, and way before run time. Your <c>eval</c> happens at run time, so too late to effect attribute processing.</p>
<p>It is in fact possible to alter when processing happens for particular attributes, but it needs to be one of the compilation phases (BEGIN, CHECK, INIT or END), and not runtime.</p>
<center><p>* * *</p></center>
<p>As it happens I've been working on some aspect-oriented programming stuff for Moose that might be just what you need.</p>
<code>
{
package User;
use Moose;
has name => (is => 'ro', isa => 'Str');
sub login {
my $self = shift;
print $self->name, " is logged in\n";
}
}
{
package Tracing;
use MooseX::Aspect;
my $aspect = __PACKAGE__;
sub log_msg {
my $class = shift;
print STDERR "TRACE: $_\n" for @_;
}
apply_to 'User' => role {
before login => sub {
my $self = shift;
$aspect->log_msg($self->name . " attempted to log in");
};
};
}
# try setting tracing to 0 :-)
my $config = { tracing => 1 };
if ($config->{tracing}) {
Tracing->setup;
}
my $bob = User->new( name => 'Bob' );
$bob->login;
</code>
<p>Packages of interest: [mod://Moose], [mod://MooseX::Aspect], [mod://Sub::Talisman] and [mod://MooseX::ModifyTaggedMethods].</p>
<p>MooseX::Aspect is still at a very early stage of development, and bugs abound. But I think it shows quite a bit of promise for doing this sort of thing.</p>
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<small><small>
<tt>perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
</tt></small></small>
</div></div>
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