Question

我正在玩创建DSL。我使用http://jroller.com/rolsen/entry/building_a_dsl_in_ruby作为指南。

鉴于此DSL：

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

有没有办法确保至少调用一次question（），右（）恰好一次和错误（）n次或多次调用？

Answer 1

不确定。只需添加一行

即可

(@question_count ||= 0) += 1

显示question方法的当前实现（对right和wrong类似），然后检查这些变量。

Answer 2

以下代码中缺少对回答的处理，但您只能控制一个正确答案

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

现在，您可以使用块语法定义问题：

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

您也可以使用其他问题定义：

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

执行方法调用

2 个答案: