ruby – 如何使用case语句返回哈希？

发布时间：2020-12-17 01:25:41 所属栏目：百科来源：网络整理

导读：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,但它总是返回nil.有什么想法吗？我使用的是Ruby 1.8.7 p35

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,但它总是返回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

解决方法

如果要在每个when子句中使用表达式,则需要使用裸case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 - 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

（编辑：李大同）

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