Make an Iterator

gistfile1.rb

 
# Here's my method that loops over a collection and yields a block
def tardies_for_student(student_id, now=Time.zone.now)
  submissions_by_student_id[student_id].each do |submission|
    assignment = @assignments_by_id[submission.assignment_id]
    yield build_tardy(assignment, submission, now)
  end
end

# now I know I can do this...

tardies_for_student(1) do |tardy|
  # do something with tardy
end

# but I want to be able to do this...

tardies_for_student(1).each do |tardy|
  # do something with tardy
end

# OR

tardies_for_student(1).map do |tardy|
  # do something with tardy
end

class TardiesForStudent
  include Enumerable

  def initialize(student_id, now = Time.zone.now)
     @submissions = submissions_by_student_id[student_id]
     @now = Time.zone.now
  end

  def each
    @submissions.each do |submission|
      assignment = @assignments_by_id[submission.assignment_id]
      yield build_tardy(assignment, submission, now)
    end
  end
end