define_method

Write methods from data — no repetition

define_method creates a method at runtime from a name and a block. Instead of hand-writing five nearly-identical predicates, you generate them from a list. This is the other half of metaprogramming: send calls methods dynamically, define_method defines them dynamically.

In an interview, say: "define_method generates methods from data at load time, so a list of statuses becomes a set of predicate methods with no duplication. It's exactly how ActiveRecord's enum gives you confirmed? and cancelled? for free."