generate.rb

Observable.generate do
  initial_state 0
  condition {|x| x <= 3}
  result_selector {|x| x + 1}
  iterator {|x| x }
  scheduler RX::TestScheduler.new
end

# OR

Observable.generate do
  initial_state 0
  iterate_while {|x| x <= 3}
  select_result_with {|x| x + 1}
  iterate_with {|x| x }
  scheduler RX::TestScheduler.new
end