排序散列Ruby中的陣列（由存在任選鍵+值分選）

Question

得到一個Ruby陣列等：

[ { "lat" => 123, "lon" => 456 }, 
    { "lat" => 789, "lon" => 102, "col" => "red" }, 
    { "lat" => 442, "lon" => 342 } ] 

我想對它進行排序，使得任何散列與col作爲密鑰意願被推到陣列的頂部或底部。

找不到正確的sort_by語法/語義。

Answer 1

a = [ { "lat" => 123, "lon" => 456 }, 
    { "lat" => 789, "lon" => 102, "col" => "red" }, 
    { "lat" => 442, "lon" => 342 } ] 

如果你想要把它們放在上面，然後

a.partition{|h| h.key?("col")}.flatten 

如果你想把它們放在底部，然後由鐵皮人建議，

a.partition{|h| h.key?("col").!}.flatten 

Answer 2

我喜歡的功能更多的方法：

require 'pp' 

a = [ {:foo => "aa","col" => "bar"}, { "lat" => 123, "lon" => 456 }, 
    { "lat" => 789, "lon" => 102, "col" => "red" }, 
    { "lat" => 442, "lon" => 342 } ] 

arr = a.group_by{|h| h.key?("col")} 

pp arr[false] + arr[true] # on the bottom 

輸出：

[{"lat"=>123, "lon"=>456}, 
{"lat"=>442, "lon"=>342}, 
{:foo=>"aa", "col"=>"bar"}, 
{"lat"=>789, "lon"=>102, "col"=>"red"}] 

---

pp arr[true] + arr[false] #on the top 

輸出：

[{:foo=>"aa", "col"=>"bar"}, 
{"lat"=>789, "lon"=>102, "col"=>"red"}, 
{"lat"=>123, "lon"=>456}, 
{"lat"=>442, "lon"=>342}]