An elegant way of assiging in ruby

Question

Is there a more elegant way of doing this logic in ruby

a = nil #=> obviously 'a' can have value but I am just setting it nil to make the eg more clear
b = a
unless b
  b = "value"
end

so that we have the value of b set in the end. We could have another variation of the above code like so

a = nil
b = a
b ||= "value"

and I can also use ternary statement to write the above code like

b = a ? a : "value"

but if you replace variable a and "value" with a long line of code then this ternary statement will start looking ugly too.

Can the above logic be made more elegant / expressive somehow or are we limited to just the above solutions?

Answer 1

b ||= "value" is much like Perl's widely-loved // and //= operators, because in Ruby the only thing that tests false is nil (and, well, false). This makes it functionally identical to Perl's //= operator. How much more "elegant" can you get than a ||= b? Honestly, I don't know how much more compactly that idea can be conveyed other than making the operator shorter (and at that point you're just being silly).

Answer 2

You almost answered your question yourself.

b = a
b ||= "value"

can be shortened to

b = a || "value"

Answer 3

I dislike using the || operator for the reason Farrel pointed out in ib's answer. It may be right here, but I'm always frightened it will trip me up one day. So I'm afraid I tend to go for the rather pedestrian:

b = "value"; b = a unless a == nil

Not pretty, I know, but safe and very, very explicit.