CODEWITHSUNDEEP
ruby
Tom Lehman
Tom Lehman

Reputation: 89233

Test whether a variable equals either one of two values

I want to test whether a equals 1 or 2

I could do

a == 1 || a == 2

but this requires repeating a (which would be annoying for longer variables)

I'd like to do something like a == (1 || 2), but obviously this won't work

I could do [1, 2].include?(a), which is not bad, but strikes me as a bit harder to read

Just wondering how do to this with idiomatic ruby

Upvotes: 61

Views: 31408

Answers (8)

esbanarango
esbanarango

Reputation: 1637

Include is definitely the way to go here. 🤝

  %w[cat dog].include?(type)

Upvotes: 3

Gourav
Gourav

Reputation: 576

You can just use intersection like

([a] & [1,2]).present?

a alternative way.

Upvotes: 5

Arcolye
Arcolye

Reputation: 6958

One way would be to petition "Matz" to add this functionality to the Ruby specification.

if input == ("quit","exit","close","cancel") then
  #quit the program
end

But the case-when statement already lets you do exactly that:

case input when "quit","exit","close","cancel" then 
  #quit the program
end

When written on one line like that, it acts and almost looks like an if statement. Is the bottom example a good temporary substitution for the top example? You be the judge.

Upvotes: 10

Paige Ruten
Paige Ruten

Reputation: 176675

First put this somewhere:

class Either < Array
  def ==(other)
    self.include? other
  end
end

def either(*these)
  Either[*these]
end

Then, then:

if (either 1, 2) == a
  puts "(i'm just having fun)"
end

Upvotes: 7

Shadowfirebird
Shadowfirebird

Reputation: 757

Maybe I'm being thick here, but it seems to me that:

(1..2) === a

...works.

Upvotes: -1

ghostdog74
ghostdog74

Reputation: 342423

a.to_s()=~/^(1|2)$/

Upvotes: 2

Jack Chu
Jack Chu

Reputation: 6821

I don't know in what context you're using this in, but if it fits into a switch statement you can do:

a = 1
case a
when 1, 2
  puts a
end

Some other benefits is that when uses the case equality === operator, so if you want, you can override that method for different behavior. Another, is that you can also use ranges with it too if that meets your use case:

when 1..5, 7, 10

Upvotes: 12

Peter
Peter

Reputation: 132247

Your first method is idiomatic Ruby. Unfortunately Ruby doesn't have an equivalent of Python's a in [1,2], which I think would be nicer. Your [1,2].include? a is the nearest alternative, and I think it's a little backwards from the most natural way.

Of course, if you use this a lot, you could do this:

class Object
  def member_of? container
    container.include? self
  end
end

and then you can do a.member_of? [1, 2].

Upvotes: 39

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