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Re: custom accessor_metaclass override of _inline_store (Moose 1 to2)

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Dave Rolsky
March 15, 2016 16:14
Re: custom accessor_metaclass override of _inline_store (Moose 1 to2)
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On Tue, 15 Mar 2016, Toby Blake wrote:

> I'm trying to convert an existing project to Moose 2 (from Moose 1.15).
> I've run into a tricky issue where the original author of the project (not
> me!) has overridden part of Moose's private API - this part has now
> changed.  I'll try and explain the situation briefly, in the hope that
> somebody can advise:
> We have an attribute trait which uses a custom accessor_metaclass.
> This accessor metaclass extends 'Moose::Meta::Method::Accessor' and
> overrides _inline_store, like this:
> override _inline_store => sub {
>  my ($self, $instance, $value) = @_;
>  my $attr = $self->associated_attribute;
>  if ($attr->has_logger) {
>     return sprintf('$attr->logger->($attr, %s, %s);', $instance, $value) . super;
>  }
>  return super;
> };
> So, essentially, it puts a call to the attribute trait's $attr->logger
> subroutine in the chain when setting a value (this is needed because we
> have code here which needs to know when an object's attribute values have
> changed - this is the function of the "logger").  And of course this code
> doesn't work with Moose 2, as there is no longer an _inline_store method in
> Moose::Meta::Method::Accessor.
> The lesson here is that we shouldn't be using parts of the private api, as
> they may change.  However, I would like to get this working without
> rewriting large chunks of it.  I naively tried changing _inline_store to
> _inline_store_value for Moose 2, but this doesn't appear to be called in
> the same way.

I think you can override Moose::Meta::Attribute->_inline_instance_set. 
This will work for any attribute that doesn't have an initializer (but no 
one uses that Moose feature).



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