Example quiz

quiz.rb

class Quiz
  attr_accessor :questions, :correct, :incorrect

  def initialize
    self.questions = []
  end

  def add_question(*args)
    self.questions << Question.new(*args)
  end

  def run
    questions.each do |question|
      question.display
      question.get_answer
    end

    self.correct, self.incorrect = questions.partition { |question| question.correct }

    display_result
    end_game
  end

  def display_result
    puts "\nYou correctly answered #{correct.size} question(s) out of #{questions.size}"
  end

  def end_game
    puts "\n\nThanks for playing, see you next time!"
  end
end

class Question
  attr_accessor :question, :op1, :op2, :op3, :op4, :answer, :answered_with, :correct

  def initialize(question, op1, op2, op3, op4, answer)
    self.question = question
    self.op1      = op1
    self.op2      = op2
    self.op3      = op3
    self.op4      = op4
    self.answer   = answer
  end

  def get_answer
    self.answered_with = gets.chomp!.strip.downcase
    self.correct       = answered_with == answer
  end

  def display
    puts '', question, op1, op2, op3, op4, ''
    puts "Type a letter (a, b, c, d) for your answer"
  end
end

quiz = Quiz.new

quiz.add_question(
  "How many places are called Paris in the US?",
  "a. 17",
  "b. 6",
  "c. 25",
  "d. 12",
  "a"
)

quiz.add_question(
  "What is Uzbekistan's capital city?",
  "a. Qarshi",
  "b. Tashkent",
  "c. Bukhara",
  "d. Nukus",
  "b"
)

quiz.add_question(
  "What is the most spoken language in Africa?",
  "a. Swahili",
  "b. French",
  "c. Arabic",
  "d. English",
  "d"
)

quiz.run