如何返回带有 case 语句的哈希？答案

【问题标题】：How do I return a hash with a case statement?如何返回带有 case 语句的哈希？
【发布时间】：2013-03-29 18:53:55
【问题描述】：

我正在尝试编写一个获取日期的天数的函数，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日期的哈希：

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

我不太清楚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

【问题讨论】：

标签： ruby hashmap

【解决方案1】：

如果要在每个 when 子句中使用表达式，则需要使用纯 case 语句。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、更正确：

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

【讨论】：

Rein 的实现很好，所以请随意忽略我的回答 :)

【解决方案2】：

您只需要稍微调整一下语法。从date = case days 语句中删除days。否则，您的条件语句将与 days 变量进行比较。

【讨论】：