perl - Using Moose, how do I set the value of a 'ro' Attribute Trait, in runtime? -

i've got attribute trait want set on basis of other class attributes. realy want default on attribute trait gets copy of class $self , not meta attribute. want in class:

after 'build' => sub {                                                        $self = shift;                                                           $self->meta->get_attribute('id')->column_name( $self->_unique_key_name ); };   

but, want keep attribute trait ro? possible. know mop allows 1 set value of class-attribute, can't figure out how set attribute on meta-attribute.

this sounds odd design (why metaclass need instance of class describing?) -- can enough using metaclass of metaclass (remember moose meta classes bootstrapped using mop itself):

$self->meta->meta->get_attribute("foo")->default($some_value); 

also remember defaults need wrapped in coderef if references themselves: $some_value = sub { $instance };

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actually, won't work - 'default' read only. rather fiddling mop @ such low level, urge reconsider design - e.g. store 'default' in attribute, , writing default sub delegated it:

package myapp::meta::attribute::trait::foo;  # set @ runtime, when have instance store here has _default_of_foo => (     => 'rw', isa => 'object', ); has foo => (     => 'ro', isa => 'object',     lazy => 1,     default => sub { shift->_default_of_foo }, );