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，但它始终返回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

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

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

Answer 2

你只需要一个小的语法调整。从days语句中删除date = case days。否则，您的条件语句将与days变量进行比较。

如何返回带有case语句的哈希？

2 个答案: