从 Elixir 地图中选择的构建选项

Question

假设这个数据集，

 %{"ACTION" => "avail.datacenters",
"DATA" => [%{"ABBR" => "dallas", "DATACENTERID" => 2,
  "LOCATION" => "Dallas, TX, USA"},
%{"ABBR" => "fremont", "DATACENTERID" => 3,
  "LOCATION" => "Fremont, CA, USA"},
%{"ABBR" => "atlanta", "DATACENTERID" => 4,
  "LOCATION" => "Atlanta, GA, USA"},
%{"ABBR" => "newark", "DATACENTERID" => 6, "LOCATION" => "Newark, NJ, USA"},
%{"ABBR" => "london", "DATACENTERID" => 7,
  "LOCATION" => "London, England, UK"},
%{"ABBR" => "tokyo", "DATACENTERID" => 8, "LOCATION" => "Tokyo, JP"},
%{"ABBR" => "singapore", "DATACENTERID" => 9,
  "LOCATION" => "Singapore, SG"},
%{"ABBR" => "frankfurt", "DATACENTERID" => 10,
  "LOCATION" => "Frankfurt, DE"},
%{"ABBR" => "shinagawa1", "DATACENTERID" => 11,
  "LOCATION" => "Tokyo 2, JP"}], "ERRORARRAY" => []}}

在 Ruby 中，我可以做到

formatted_array_of_hashes = data_set.each.map{ |h| { h["LOCATION"] => h["DATACENTERID"] }}

然后

merged_hash = Hash[*formatted_array_of_hashes.map(&:to_a).flatten]

...我将在选择标签中使用位置、数据中心 ID。

请问我如何在 Elixir 中实现类似的功能？

任何指向正确方向的指针都将受到高度赞赏

Answer 1

你可以使用for，在do中返回一个2元组，然后放到into: %{}：

map = for %{"LOCATION" => k, "DATACENTERID" => v} <- data_set, into: %{}, do: {k, v}

如果您想将其与Phoenix.HTML.Form.select/4 一起使用，则无需构建地图。您可以传递元组列表。这样您就不会像使用地图一样丢失元素的顺序，因为地图是无序的。

select _, _, for(%{"LOCATION" => k, "DATACENTERID" => v} <- data_set, do: {k, v})

---

旁注：您的 Ruby 代码也可以简化为：

hash = data_set.map { |h| [h["LOCATION"], h["DATACENTERID"]] }.to_h