Today I Learned

hashrocket A Hashrocket project

Quickly find module inclusion in Ruby

Given I have a class like so:

class Location < ActiveEnum::Base
  include WithLabel

Normally I would check for inclusion of something via a declarative method like:

=> true

=> false

=> true

However it never occured to me that < is defined on Class and returns true if is a subclass of the requested module.

So we can do something like this now:

Location < ActiveEnum::Base
=> true

Location < String
=> nil

Location < WithLabel
=> true

Subtle difference is that the ‘falsey’ case returns nil instead of false.

Also the definition of this method states that it returns true if module is a subclass of other but I’ve found that it returns true for methods that are included as well. Take that as you will.

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