School.domain.rb

school.domain.rb

class School
  attr_reader :roster

  def initialize(school_name)
    @roster = {}
    @name = school_name
  end

  def add_student(stu_name, grade)
    (self.roster[grade] && (self.roster[grade] << stu_name)) ||
      self.roster[grade] = [stu_name]
  end

  def grade(num)
    self.roster[num]
  end

  def sort
    self.roster.keys.sort.inject({}) do |hash, grade|
      hash[grade] = self.roster[grade].sort
      hash
    end
  end
end