Local Jump Error No block given (yield) error on find_each

I'm trying to step through a list of records that are retrieved with find_each.

I patterned my controller code on the answer in this stack overflow post, but I'm still getting a "No Block Given (Yield)" error.

I'm just getting started in Ruby and Rails and I haven't yet found a full fledged explanation (lots of basic examples though) of blocks and yield that gives me what I need.

My code looks like this:

def select_save
    @class = params[:class]
    @student_id = params[:id]
    @class.each do |id|
      old_subject = Subject.find(id)
      new_subject = old_subject.dup
      new_subject.student_id = @student_id
      new_subject.save
      Assignment.find_each.where(:subject_id => id) do |assignments|
        assignments.each do |a|
          new_assignment = a.dup
          new_assignment.subject_id = new_subject.id
          new_assignment.save
        end
      end
    end

    respond_to do |format|
      format.html { redirect_to @student, :notice => 'Subject and assignments created.' }
    end
  end

and the error points to the line with find_each.

I know I need a block to yield to, but how exactly that would look in this particular case escapes me.

Thanks for any suggestions.