如何返回带有case语句的哈希？

Question

我正在尝试编写一个函数,该函数采用日期的日期编号,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日期的哈希:

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

我无法弄清楚这段代码有什么问题,但它总会返回nil.有什么想法吗？我使用的是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

case如果要在每个when子句中使用表达式,则需要使用bare 语句.否则,Ruby将调用(days <= 31) === days,这将永远不会成立.

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,这种实现忽略了闰日,这样做似乎更简单,更正确:

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