使用 Ruby 在日期范围之间选择数组 [英] Select arrays between date ranges with Ruby

问题描述

我有一个数组数组，我想选择日期落在某个范围内的数组.

I have an array of arrays, I want to select arrays with a date that falls in a certain range.

ar = [[72162, "2014-01-21"], 
[53172, "2014-01-22"], 
[49374, "2014-01-23"], 
[41778, "2014-01-24"], 
[34182, "2014-01-25"], 
[58869, "2014-01-26"], 
[72162, "2014-01-27"], 
[43677, "2014-01-28"], 
[37980, "2014-01-29"], 
[87354, "2014-01-30"], 
[43677, "2014-01-31"]]

例如，我想获取 2014-01-24 和 2014-01-29 之间的所有数组.

For example, I'd like to get all arrays between 2014-01-24 and 2014-01-29.

推荐答案

不使用Date:

ar.select { |_,d| d >= "2014-01-24" && d <= "2014-01-29" }

=> [[41778, "2014-01-24"],
    [34182, "2014-01-25"],
    [58869, "2014-01-26"],
    [72162, "2014-01-27"],
    [43677, "2014-01-28"],
    [37980, "2014-01-29"]]

或

ar.select { |_,d| ("2014-01-24".."2014-01-29").cover?(d) }

请注意，这取决于以年-月-日顺序表示的日期.

Note this depends on the date being expressed in year-month-day order.

我以前使用过我认为是 Range#include?，但@toro2k 指出这实际上是 Enumerable#include?，这很慢.我原以为 Range#include? 只能比较端点，因为 <=> 是为字符串定义的.不是这样；它仅适用于值是数字或单个字符串时(否则 super 到 Enumerable#include?).这让我很困惑.对于任何有兴趣的人，我想我现在明白限制申请的原因了.

I formerly used what I thought was Range#include?, but @toro2k pointed out that is was actually Enumerable#include?, which is quite slow. I had thought that Range#include? would be able to just compare endpoints, since <=> is defined for Strings. Not so; it only applies when the values are numeric or single character strings (else it supers to Enumerable#include?). That puzzled me. For anyone interested, I think I now understand the reason for the restricted application.

我们希望 ('aa'..'zz').include?('mno') 的行为与

We would want ('aa'..'zz').include?('mno') to behave the same as

('aa'..'zz').to_a.include?('mno') => false

假设我们这样做:

class String
  alias :spaceship :<=>
  def <=>(other)
    spaceship(other.size > 1 ? other[0,2] : other)
  end
end

然后

"mno" >= 'aa' # => true
"mno" <= 'zz' # => true

所以如果 Range#include? 只考虑端点，

so if Range#include? only considered the endpoints,

('aa'..'zz').include?("mno") # => true

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