ruby - 如何返回带有 case 语句的散列？

Question

我正在尝试编写一个函数来获取日期的天数，例如，今天(3 月 29 日)是一年中的第 88 天。然后它返回一个包含月份和月份中的日期的散列:

{"month" => "March, "day" => 29}

我不太明白这段代码有什么问题，但它总是返回nil。有什么想法吗？我正在使用 Ruby 1.8.7 p358。

def number_to_date(days)
  date = case days
    when days <= 31  then {"month" => "January",   "day" => days}
    when days <= 59  then {"month" => "February",  "day" => (days - 31)}
    when days <= 90  then {"month" => "March",     "day" => (days - 59)}
    when days <= 120 then {"month" => "April",     "day" => (days - 90)}
    when days <= 151 then {"month" => "May",       "day" => (days - 120)}
    when days <= 181 then {"month" => "June",      "day" => (days - 151)}
    when days <= 212 then {"month" => "July",      "day" => (days - 181)}
    when days <= 243 then {"month" => "August",    "day" => (days - 212)}
    when days <= 273 then {"month" => "September", "day" => (days - 243)}
    when days <= 304 then {"month" => "October",   "day" => (days - 273)}
    when days <= 334 then {"month" => "November",  "day" => (days - 304)}
    when days <= 365 then {"month" => "December",  "day" => (days - 334)}
  end
  return date
end

Answer 1

你需要使用裸case如果你想在每个 when 中使用表达式条款。否则，Ruby 将调用 (days <= 31) === days ，这永远不会是真的。

def number_to_date(days)
  date = case
    when days <= 31  then {"month" => "January",   "day" => days}
    when days <= 59  then {"month" => "February",  "day" => (days - 31)}
    # ...
  end
  return date
end

然而，这个实现忽略了闰日，这样做似乎更简单也更正确:

def number_to_date(days)
  date = Date.ordinal(Date.today.year, days)
  {"month" => Date::MONTHNAMES[date.month], "day" => date.day}
end