ruby-on-rails - 为什么介于两者之间？ ruby 中 Date 和 DateTime 的工作方式不同？

Question

doc说:

between?(min, max) public

Returns true if the current object’s time is within the specified min and max time.

在 ruby 中:

>> DateTime.now.between?(DateTime.now, DateTime.now+1)
=> false
>> Date.today.between?(Date.today, Date.today+1)
=> true

通过使用 .current在 Rails 中，差异变得更加明显，因为您特别假设此方法在 DateTime 上会有类似的行为。和 Date :

>> DateTime.current.between?(DateTime.current, DateTime.current+1)
=> false
>> Date.current.between?(Date.current, Date.current+1)
=> true

这是故意的行为吗？如果是这样，为什么？处理 min 时的行为似乎很奇怪区间的边缘是没有异质性的。特别是考虑到 max部分是特殊的:

>> DateTime.now.between?(DateTime.now-1, DateTime.now)
=> true
>> Date.today.between?(Date.today-1, Date.today)
=> true

Answer 1

让我们启动 irb 并运行这些代码:

"#{DateTime.now.inspect} \n #{DateTime.now.inspect}"

结果会是这样的:

#<DateTime: 2017-03-22T11:42:28+03:00 ((2457835j,31348s,373353553n),+10800s,2299161j)>
#<DateTime: 2017-03-22T11:42:28+03:00 ((2457835j,31348s,373449152n),+10800s,2299161j)>

如您所见，以纳秒为单位存在差异 (373353553n < 373449152n)

假设 difference 等于“x”，而 DateTime.now 等于“Now”，那么:

1) DateTime.now.between?(DateTime.now, DateTime.now+1.second)

Now.between?(Now+x, Now+x+x+1.second) => false

2) DateTime.now.between?(DateTime.now-1, DateTime.now)

Now.between?(Now+x-1.second, Now+x+x) => true