My 'read-only' objects now have their very own metadata class. Trying
to update from the 'save', 'insert', 'update', etc. now fails. I also
have the accessors throwing Exception::Class objects if someone tries
to set an attribute value. However, it's a nasty hack because the
other code examples I saw here were failing:
sub add_columns {
my ( $self, @columns ) = @_;
$self->SUPER::add_columns(@columns);
my $class = $self->class;
foreach my $column ( $self->columns ) {
$column->add_trigger(
event => 'on_set',
code => sub {
my ($called_from) = caller(1);
my $attribute = $class->_attribute_name($column);
return if $called_from eq 'Rose::Object';
throw_read_only "Attribute '$attribute' is read-only";
},
);
}
}
(I don't rely on the return value of
$self->SUPER::add_columns(@columns) because we're only using the CPAN
version)
Note the 'return' condition. I found that if I didn't have that in,
the following would throw an exception:
my $os = Donhost::OS->new( os => 'ubuntu' );
The hack guarantees that only things like the following throwing
exceptions:
$os->os('windows');
$os->description('sucks');
The hack relies on the order of call stack frames being different when
I'm constructing an object or just setting an accessor directly. How
can I do this without relying on the internals like this?
Cheers,
Ovid
--
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