|P is for Practical|
Moose and default valuesby morgon (Deacon)
|on Feb 20, 2013 at 22:13 UTC||Need Help??|
morgon has asked for the
wisdom of the Perl Monks concerning the following question:
assume you have a script that takes input from the command-line and passes that on to a Moose-class Foo, i.e.
When no bar-value is supplied on the command-line the class should use a default instead (I want to keep the defaults in the class-definition not in the script).
A first try does not what I want:
because then when the command-line is empty the constructor is called with "bar" => undef, setting the attribute to undef and not to the intended default.
I usually do this instead:
This does work, instantiating via Foo->new( bar => undef ) sets bar to the default, but the downside is that the default-value is not declared with the attribute but buried in the BUILDer-code and to make this work the attribute has to be "rw".
So I wonder if there is a better way to achieve this - i.e. declaratively defining attribute-defaults for ro-attributes that also get applied when undef is passed in.