Question

Is there an elegant way to write

  if o.class == ClassA or o.class == ClassB or o.class == ClassC

I’m not specifically looking to compare classes, it was just an example where I wasn’t doing things with booleans so I can’t do something like

  if o.class == (ClassA or ClassB or ClassC)

Other examples are

  if string == "asdf" or string == "1337"

The only thing that I’ve found seems to be

  if [ClassA, ClassB, ClassC].include? o.class

or

  if ["asdf", "1337"].include? string

Answer 1

I think the most elegant solution is the one you already provided, which is using ‘include?’.

Just for the sake of variety, you also have the option of using a case when:

case o
  when ClassA, ClassB, ClassC
  ...

Another alternative, which I believe is just a tad more readable than ‘include?’ is to create your own ‘in?’, for example:

class Object
  def in?(array)
    array.include? self
  end
end

and then you can use

if o.class.in? [ClassA, ClassB, ClassC]