When is the Enumerator::Yielder#yield method useful?

Question

The question \"Meaning of the word yield\" mentions the Enumerator::Yielder#yield method. I haven\'t used it before, and wonder under what circumstances it would be

Answer 1

For example you can use it to construct Rack response bodies inline, without creating classes. An Enumerator can also work "outside-in" - you call Enumerator#each which calls next on the enumerator and returns every value in sequence. For example, you can make a Rack response body returning a sequence of numbers:

run ->(env) {
  body = Enumerator.new do |y|
   9.times { |i| y.yield(i.to_s) }
  end
  [200, {'Content-Length' => '9'}, body]
}