Appalling Farrago

A blog about stuff

Ruby's && operator for params

03 Nov 2013

I was reading through some ruby code and I found a cute little shortcut for avoiding lookups on those frustrating nil objects. The code is question was:

def search_value
  params[:search] && params[:search][:value]
end

This comes from the excellent geocoding on rails. What’s so cool about this is it will return the first value if it is falsey otherwise it will return whatever the second value is. It can do this through the magic of short circuit evaluation.

What this means is that ruby is smart enough to know that if the first value is falsey then it doesn’t even need to check what the second value is. If the first value is false then && (and) will always evaluate to falsey. If the first value is truthy then whatever the second value is (truthy or falsey) that will also be what the && should evaluate to. So it simply returns that second value.

I love this elegance. I just wished I found it sooner -_-

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