根据某些元素中可能为零的属性对数组进行排序 [英] Sorting an array based on an attribute that may be nil in some elements
问题描述
我有一个对象数组
[<#a star=1 val=1>, <#a star=nil val=3> , <#a star=2 val=2>]
我需要数组按时间排序,然后按 val
i need the array to be sorted by time, then by val
[ <#a star=2 val=2>, <#a star=1 val=1>, <#a star=nil val=3> ]
但是使用 sort_by 会抛出错误,因为时间为零.
but using the sort_by throws an error because the time is nil.
我现在正在使用一种丑陋的排序方式,但我相信有一个很好的方法来解决它
I am using an ugly way to sort right now, but i am sure there is a nice way to go about it
starred=[]
@answers.each {|a| (starred << a) if a.starred }
@answers=@answers-starred
starred=starred.sort_by {|a| a.starred }.reverse
@answers=starred+@answers
推荐答案
starred.sort_by { |a| [a ? 1 : 0, a] }
当它必须比较两个元素时,它比较一个数组.当 Ruby 比较数组时(调用 ===
方法),它比较第一个元素,只有当第一个元素相等时才去比较第二个元素.<代码>?1 : 0 保证,我们将 Fixnum 作为第一个元素,所以它应该没有错误.
When it has to compare two elements, it compares an arrays. When Ruby compares arrays (calls ===
method), it compares 1st element, and goes to the 2nd elements only if the 1st are equal. ? 1 : 0
garantees, that we'll have Fixnum as 1st element, so it should be no error.
如果你做?0 : 1
, nil
将出现在数组的末尾而不是开头.
下面是一个例子:
If you do ? 0 : 1
, nil
will appear at the end of array instead of begining.
Here is an example:
irb> [2, 5, 1, nil, 7, 3, nil, nil, 4, 6].sort_by { |i| [i ? 1 : 0, i] }
=> [nil, nil, nil, 1, 2, 3, 4, 5, 6, 7]
irb> [2, 5, 1, nil, 7, 3, nil, nil, 4, 6].sort_by { |i| [i ? 0 : 1, i] }
=> [1, 2, 3, 4, 5, 6, 7, nil, nil, nil]
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