Enforcing method calls

I am playing around with creating a DSL. I am using http://jroll开发者_运维问答er.com/rolsen/entry/building_a_dsl_in_ruby as a guide.

Given this DSL:

question 'Who was the first president of the USA?'
wrong 'Fred Flintstone'
wrong 'Martha Washington'
right 'George Washington'
wrong 'George Jetson'

is there a way to make sure that question() is called at least once, right() exactly once and wrong() n or more times?

---

Sure. Just add the line

(@question_count ||= 0) += 1

to whatever your current implementation of the question method looks like (and similarly for right and wrong) and then check those variables.

---

The handling of answering is missing in the following code, but you have control of only one right answer

class Question
  def initialize(text)
    @text = text
    @answers = []
    @correct = nil #index of the correct answer inside @answers
  end
  def self.define(text, &block)
    raise ArgumentError, "Block missing" unless block_given?
    q = self.new(text)
    q.instance_eval(&block)    
    q
  end
  def wrong( answer )
    @answers << answer
  end
  def right(answer )
    raise "Two right answers" if @correct
    @answers << answer
    @correct = @answers.size
  end
  def ask()
    puts @text
    @answers.each_with_index{|answer, i|
      puts "\t%2i %s?" % [i+1,answer]
    }
    puts "correct is %i" % @correct
  end
end

def question( text, &block )
  raise ArgumentError, "Block missing" unless block_given?
  Question.define(text, &block)
end

Now you can define your question with block syntax:

question( 'Who was the first president of the USA?' ) {
  wrong 'Fred Flintstone'
  wrong 'Martha Washington'
  right 'George Washington'
  wrong 'George Jetson'
}.ask

You may use also another definition of questions:

q = Question.new( 'Who was the first president of the USA?' )
q.wrong 'Fred Flintstone'
q.wrong 'Martha Washington'
q.right 'George Washington'
q.wrong 'George Jetson'
q.ask