Ruby equivalent of Groovy's Elvis (?:) operator?

Question

I know I can live without it, but the question's been bugging me.

Is there a Ruby idiom that's equivalent to Groovy's Elvis operator (?:)?

Essentially, I want to be able to shorten this

PARAM = ARGV[0] ? ARGV[0] : 'default'

Or equivalently

PARAM = 'default' unless PARAM = ARGV[0]

Into something like this

PARAM = ARGV[0] ?: 'default'

possible duplicate of [What does ||= mean in Ruby?](http://stackoverflow.com/questions/995593/what-does-mean-in-ruby) — Andrew Grimm, Oct 19 '11 at 03:53

Alistair A. Israel · Accepted Answer · 2011-10-19T04:23:59.487

60

Never mind :-) I just found the answer myself after finding out the name of the operator.

From here:

PARAM = ARGV[0] || 'default'

(Must be 'cause I'm juggling 4 languages right now so I forgot I could do that in the first place.)

edited Oct 19 '11 at 04:23

answered Oct 19 '11 at 02:52

4

Alternatively, if you're doing something like `@params = @params || 5 `you can shorten it to `@params ||= 5` – Ryan Bigg Oct 19 '11 at 02:58
3

@RyanBigg: To be pedantic, it's more like `@params || @params = 5`. http://stackoverflow.com/questions/995593/what-does-mean-in-ruby/2505285#2505285 – Andrew Grimm Oct 19 '11 at 03:58
8

This is sadly not entirely true. Kotlin's `?:` and C#'s `??` check for NULLITY. Ruby's `||` checks for truth-iness. If you are working with booleans, let's say `foo = bar || true` and you are expecting `true` to be the default only if `bar` is `nil`, it won't work. If `bar` is not `nil` but `false`, it will still default to `true`. – Adeynack May 06 '19 at 12:30

score 8 · Answer 2 · answered Jul 14 '20 at 13:14

8

Possible since Ruby 2.3.

dog&.owner&.phone

answered Jul 14 '20 at 13:14

Jacka

1

It solves a different problem, but this gets around the `null`-ity vs `true`-thy conundrum:, `nil.class # => NilClass`, `nil&.class # => nil (not NilClass!)`, `false.class #=> FalseClass`, `false&.class #=> FalseClass` – Alistair A. Israel Sep 11 '20 at 16:44

score 4 · Answer 3 · answered Oct 19 '11 at 02:53

4

Isn't PARAM = ARGV[0] ? ARGV[0] : 'default' the same as PARAM = (ARGV[0] || 'default') ?

answered Oct 19 '11 at 02:53

Hock

Check [this comment](https://stackoverflow.com/questions/7816032/ruby-equivalent-of-groovys-elvis-operator#comment98655983_7816041). It's not exactly the same. – Adeynack May 06 '19 at 12:30

3 Answers3