A Quicker Way to Compare Multiple Equals Operators in Ruby

Apr 20, 2015 Ruby

You know the typical if/else statement in Ruby, right?

if this_thing == 'cheese'
  puts 'This is cheese.'
else
  puts 'This is not cheese.'
end

Now, let's say you want to see if this_thing is "cheese" or "magical beans." Logic tells you to write something like this:

if this_thing == 'cheese' || this_thing == 'magical beans'
  puts 'This is either cheese or magical beans.'
else
  puts 'This is not cheese or magical beans.'
end

Oh, but now you need to see if you also have a meat grinder.

if this_thing == 'cheese' || this_thing == 'magical beans' || this_thing == 'meat grinder'
  puts 'This is either cheese or magical beans or a meat grinder.'
else
  puts 'This is not cheese or magical beans or a meat grinder.'
end

It gets out of hand real fast.

Solving with Regex

One solution is to write regex comparisons to the original variable, or something like this:

if this_thing =~ /^(cheese|magical\ beans|meat\ grinder)$/
  puts 'This is either cheese or magical beans or a meat grinder.'
else
  puts 'This is not cheese or magical beans or a meat grinder.'
end

That should work fine, but I don't love it when you're comparing something straightforward, like and integer or a predictable string. It works better when you're looking for part of a string or some variation in the string.

Using an Array

Instead, why not just turn the expected values into an array and then see if this_thing is in there?

if ['cheese', 'magical beans', 'meat grinder'].include?(this_thing)
  puts 'This is either cheese or magical beans or a meat grinder.'
else
  puts 'This is not cheese or magical beans or a meat grinder.'
end

Predefining the Array

And if your array gets out of hand, you can always define it elsewhere.

weird_kitchen_things = [
  'cheese',
  'magical beans',
  'meat grinder',
  'draino'
]

if weird_kitchen_things.include?(this_thing)
  puts "This is either #{weird_kitchen_things.join(' or ')}."
else
  puts "This is not #{weird_kitchen_things.join(' or ')}."
end

Notice here how we also clean up the output so we don't have to change the return every time we add a value to our array.

Did you learn something or find this article interesting?

If so, why not