Overriding object methods (sometimes)

Andy Armstrong andy at hexten.net
Mon Feb 25 17:49:12 GMT 2008

On 25 Feb 2008, at 17:25, Bradley Dean wrote:

> Greetings folks,
> I've recently had cause to wrap LWP::UserAgent in a child class
> which needs to override most public methods. In doing so I've hit up
> against a problem - these requests call each other, but I only want my
> child-class methods to be called when I call them.
> My solution was to check the caller and respond appropriately, for
> instance:
> sub request {
>  my ($self, @params) = @_;
>  my ($package, $filename, $line) = caller();
>  if ( $package eq 'LWP::UserAgent' ) {
>    return $self->SUPER::request(@params);
>  }
>  else {
>    return $self->_wrapper(\&LWP::UserAgent::request, @params)
>  }
> }
> Where &_wrapper contains my local logic (it's taking a reference
> to &LWP::UserAgent::request because it's going to call it later on).
> This works fine, and isn't overly ugly, but I'm wondering if I've  
> missed or
> forgotten a nicer way to do it. :)
> Any thoughts?

It might be cleaner to make your class into a wrapper around an  
LWP::UserAgent instance rather than a subclass of it.  So that $self- 
 >SUPER::request() would become $self->{_lwp}->request(). Then LWP  
will despatch normally to its own methods.

For any methods that you want to pass through you can use AUTOLOAD or  
some similar magic.

So basically write a proxy for LWP::UserAgent.

Andy Armstrong, Hexten

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