man Aspect::AdviceContext (3): The Join Point context (DEPRECATED)

SYNOPSIS

$pointcut = call qr/^Person::[gs]et_/
& cflow company => qr/^Company::/;

# using in 'before' advice code
before {
my $context = shift; # context is only param to advice code
print $context->type; # 'before': advice type: before/after
print $context->pointcut; # $pointcut: the pointcut for this advice
print $context->sub_name; # package + sub name of matched sub
print $context->package_name; # 'Person': package name of matched sub
print $context->short_sub_name; # sub name of matched sub
print $context->self; # 1st parameter to matched sub
print $context->params->[1]; # 2nd parameter to matched sub
$context->append_param($rdbms); # append param to matched sub
$context->append_params($a, $b); # append params to matched sub
$context->return_value(4) # don't proceed to matched sub, return 4
$context->original->(x => 3); # call matched sub, don't proceed
$context->proceed(1); # do proceed to matched sub after all
print $context->company->name; # access cflow pointcut advice context
} $pointcut;

DESCRIPTION

This module has been deprecated and is included for back-compatibility. See Aspect::Point for the replacement to this module.

Advice code is called when the advice pointcut is matched. In this code, there is always a need to access information about the context of the advice. Information like: what is the actual sub name matched? What are the parameters in this call that we matched? Sometimes you want to change the context for the matched sub: append a parameter, or even stop the matched sub from being called.

You do all these things through the "AdviceContext". It is the only parameter provided to the advice code. It provides all the information required about the match context, and allows you to change the behavior of the matched sub.

Note that modifying parameters through the context, in the code of an after advice, will have no effect, since the matched sub has already been called.

CFLOW CONTEXT

If the pointcut of an advice is composed of at least one Aspect::Pointcut::Cflow, advice code may require not only the context of the advice, but also the context of the cflows. This is required if you want to find out, for example, what is the name of the sub that matched a cflow. E.g. for the synopsis example above, what method of "Company" started the chain of calls that eventually reached the get/set on "Person"?

You can access cflow context in the synopsis above, by calling:

  $context->company;

You get it from the main advice context, by calling a method named after the context key used in the cflow spec. In the synopsis pointcut definition, the cflow part was:

  cflow company => qr/^Company::/
        ^^^^^^^

An "AdviceContext" will be created for the cflow, and you can access it using the key "company".

EXAMPLES

Print parameters to matched sub:

  before { my $c = shift; print join(',', $c->params) } $pointcut;

Append a parameter:

  before { shift->append_param('extra-param') } $pointcut;

Don't proceed to matched sub, return 4 instead:

  before { shift->return_value(4) } $pointcut;

Call matched sub again, and again, until it returns something defined:

  after {
     my $context = shift;
     my $return  = $context->return_value;
     while (!defined $return)
        { $return = $context->original($context->params) }
     $context->return_value($return);
  } $pointcut;

Print the name of the "Company" object that started the chain of calls that eventually reached the get/set on "Person":

  before { print shift->company->name } $pointcut;

AUTHORS

Adam Kennedy <[email protected]>

Marcel Gru.nauer <[email protected]>

Ran Eilam <[email protected]>

COPYRIGHT