define_singleton_method.rb

class Garden
  DEFAULT_STUDENTS = %w(
    Alice Bob Charlie David
    Eve Fred Ginny Harriet
    Ileana Joseph Kincaid Larry
  )

  def initialize(garden_order, students=DEFAULT_STUDENTS)
    @garden_order = garden_order
    @students = students.map { |student| student.downcase }.sort
    @plant_hash = {
      V: :violets,
      C: :clover,
      R: :radishes,
      G: :grass
    }
    @students.each_with_index do |student, index|
      define_singleton_method student.to_sym, -> {
        convert_to_plants(index * 2)
      }
    end
  end

  def garden_rows(position)
    @garden_order.split("\n").map do |row|
      row.split("").drop(position).take(2)
    end.flatten
  end

  def convert_to_plants(position)
    garden_rows(position).map do |plant|
      @plant_hash[plant.to_sym]
    end
  end
end

method_missing.rb

class Garden
  DEFAULT_STUDENTS = %w(
    Alice Bob Charlie David
    Eve Fred Ginny Harriet
    Ileana Joseph Kincaid Larry
  )

  def initialize(garden_order, students=DEFAULT_STUDENTS)
    @garden_order = garden_order
    @students = students.map { |student| student.downcase }.sort
    @plant_hash = {
      V: :violets,
      C: :clover,
      R: :radishes,
      G: :grass
    }
  end

  def garden_rows(position)
    @garden_order.split("\n").map do |row|
      row.split("").drop(position).take(2)
    end.flatten
  end

  def method_missing(method_id, *args)
    student_place = @students.index(method_id.to_s)
    convert_to_plants(student_place * 2)
  end

  def convert_to_plants(position)
    garden_rows(position).map do |plant|
      @plant_hash[plant.to_sym]
    end
  end
end