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Re^2: Good practice for OO module defaults

by tobyink (Canon)
on Apr 09, 2019 at 15:50 UTC ( #1232355=note: print w/replies, xml ) Need Help??

in reply to Re: Good practice for OO module defaults
in thread Good practice for OO module defaults

"It's recommended to always make an Moo attribute lazy unless there's a good reason for it not to be."

Recommended by whom? Plenty of attributes simply don't have any sensible default value. For many attributes, having them unset is itself meaningful. (For example, if you object has an output_file attribute, leaving it unset might indicate that you don't want it to produce any output.) And if the default is a simple value (like 0, 1, undef, or the empty string) then making it eager (i.e. not lazy) may have performance benefits.

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Re^3: Good practice for OO module defaults
by 1nickt (Abbot) on Apr 10, 2019 at 10:53 UTC

    "... unless there's a good reason for them not to be."

    As for the recommendation, I can't find the original source but am sure I have read it in some doc somewhere. In my own experience it's usually the case that many if not most attributes depend on others or other things, and rather than try to remember all that I am lazy and use lazy and a builder. Of course that is not so in all cases, including e.g. your example of an attribute that has a static value.

    The way forward always starts with a minimal test.

      Sure, if an attribute's default value is going to be based on other attributes, then make it a lazy default. For most people, that's a minority of attributes though.

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