用空字符串最新的rails sort_by字符串

Question

 foot = [{val: "left"}, {val: "right"}, {val: nil}]
 foot.sort_by{ |f| f[:val].to_s } 
 => [{:val=>nil}, {:val=>"left"},{:val=>"right"}]

How do I sort such array descеnded with nil-elements at the end of the list? => left, right, nil

Answer 1

The most obvious thing is to separate array into 2 parts: with nil values, and the other:

foot = [{val: "left"}, {val: "right"}, {val: nil}]
nil_array, str_array = foot.partition { |h| h[:val].nil? }
str_array.sort_by{ |f| f[:val].to_s }.concat(nil_array)

If it were numbers, I would also suggested something like:

foot.sort_by { |f| f[:val] ? f[:val] : Float::INFINITY }

Answer 2

You can use sort to compare pairs of values and handle nil values explicity in the comparisons.

foot = [{val: "left"}, {val: "right"}, {val: nil}]
foot.sort{ |a,b| a[:val].nil? ? 1 : ( b[:val].nil? ? -1 : a[:val] <=> b[:val]) }
=> [{:val=>"left"},{:val=>"right"},{:val=>nil}]

Answer 3

较短的一个：

foot.sort_by { |a| [a[:val] ? '' : ' ', a[:val].to_s] }