How to call method within builder - perl

Question

I have a class with an attribute set up as follows:
has _data => (
is => 'ro',
lazy => 1,
builder => '_load',
);
sub _load {
my $self = shift;
return retrieve $self->_file;
}
However I now want to call a method already defined on the class before returning the data.
In old-school Perl OO, I'd be doing something like this:
sub _load {
# Assuming laziness is implemented somewhere else.
my $self = shift;
$self->{_data} = retrieve $self->_file;
$self->refresh; # which does something with $self->{_data}
return $self->{_data};
}
But I can't figure out a 'clean' way to do this in Moose.
I've considered the following, but think they are quite ugly, and that there must be a better way of doing this.
If I make _data read-write, I could potentially write the data to the accessor, call the method then return the value from the accessor for Moose to write back to the accessor.
If I turn it into a plain old method then I'd have to define another attribute, say _raw_data, store the data in there, modify refresh() to use that attribute, and everything else uses _data().
Violate encapsulation and access the underlying $self->{_data} directly.
I tried an after '_load' => \&refresh;, but that just created an endless loop.

Answer 1

This would be a nice use of triggers:
has _data => (
is => 'ro',
lazy => 1,
builder => '_load',
trigger => sub { shift->refresh },
);
Except that triggers don't work on default/built values - only on values passed to the constructor explicitly, or passed to a writer/accessor method. Sad face. :-(
One solution would be to rewrite your refresh method so that instead of operating on $self->_data, it can accept a parameter (perhaps falling back to operating on $self->_data if no parameter is given.
sub _load {
my $self = shift;
my $tmp = retrieve $self->_file;
$self->refresh($tmp);
return $tmp;
}
sub refresh {
my $self = shift;
my $data = scalar(#_) ? $_[0] : $self->_data;
# do something with $data
}