Conditional assignment with empty strings

Question

I love conditional assignment syntax in Ruby and use it all the time:

x = this_var || that_var

Right now I am working with several APIs, which return empty strings for non-existing values. Since empty string evaluates to true in Ruby I can no longer use the syntax above to set default values. It gets worse when I have several "levels" of defaults, e.g. "if this var doesn't exist set it to that var, if that doesn't exist too, set it to yet another var". So I end up doing this:

x = if this_var.present?
       this_var
    elsif that_var.present?
       that_var
    else
       last_resort
    end

The .present? method helps but not much. How would I write something like this in a more concise way?

I am using Rails 4 so Rails methods are welcome as an answer :)

Thanks

@sawa: to his credit, it's not always obvious which things are rails and not standard ruby. You can't expect him to add tags for all the gems in his gemfile. — Sergio Tulentsev
– Sergio Tulentsev, Commented Oct 10, 2017 at 9:48
@sawa Yeah I am using Rails but the question doesn't imply that I need a Rails method to do what I want, if there is a native Ruby one. I just happened to use a rails method in my example. I'll update the question anyway. — ivanibash
– ivanibash, Commented Oct 10, 2017 at 9:51

Stefan · Accepted Answer · 2017-10-10 11:15:44Z

11

This is where you use present?'s brother, presence (assuming you use rails or at least active support).

x = this_var.presence || that_var.presence || last_resort

edited Oct 10, 2017 at 11:15

Stefan

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answered Oct 10, 2017 at 9:45

Sergio Tulentsev

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Comments

sawa · Accepted Answer · 2017-10-10 09:58:27Z

5

x = [this_var, that_var, last_resort].find(&:present?)

answered Oct 10, 2017 at 9:58

sawa

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1 Comment

Oleksandr Holubenko Over a year ago

what about .compact.first ?)

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