Is there a "fancy" Ruby way to check whether a local variable is both defined and evaluates to true without using ands and ors?

This is quite a quick question. I currently use*

do_this if (testvar ||= false)

Which works just fine.

But this approach unnerves me because while fast, it does not short-circuit like defined?(testvar) && testvar does, and it instantiates and assigns a value to a local variable that is subsequently never used, which seems inefficient.

I enjoy the very reasonable fact that instance variables are nil before assignment, but I'd like for the situation to be just as easy for local variables.

EDIT: * – t开发者_运维问答hat's a huge lie. I don't know why I said that. I don't use testvar ||= false. That would be silly. What I have used, however, is testvar rescue false, which doesn't have nearly as many ugly side effects (does it?).

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I don't know about a "fancy" way but there's an explicit way, which is sometimes better than fancy, IMHO.

do_this if defined? testvar and testvar

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How about:

do_this unless testvar.nil?