Question

我从数据库返回了不同的结构，我想用所有自定义值（例如Ecto.Assoication.Notloaded）替换值not loaded。

这是一条记录

 unit = %{
  __meta__: #Ecto.Schema.Metadata<:loaded, "units">,
  cdc_location_class_id: nil,
  description: "",
  facility: #Ecto.Association.NotLoaded<association :facility is not loaded>,
  facility_id: 2215,
  id: 719,
  is_active: true,
  name: "Unit",
  rooms: #Ecto.Association.NotLoaded<association :rooms is not loaded>
}

这是我想要的地图

 unit = %{
  __meta__: #Ecto.Schema.Metadata<:loaded, "units">,
  cdc_location_class_id: nil,
  description: "",
  facility: "not loaded">,
  facility_id: 2215,
  id: 719,
  is_active: true,
  name: "Unit",
  rooms: "not loaded"
}

有什么建议吗？

谢谢

Answer 1

我将使用:maps.map/2，在value参数上进行模式匹配，并在必要时将其替换：

new_unit =
  :maps.map(fn
    _, %Ecto.Association.NotLoaded{} -> "not loaded"
    _, value -> value
  end, unit)

如果您需要在地图列表上运行此代码，只需将以上内容放入函数中并使用Enum.map/2。

Answer 2

由于结构只是地图，因此它们可与Map模块中的功能一起使用

因此，您可以使用Map.put替换该值。这是示例：

defmodule Test do
  defmodule User do
    defstruct name: "John", age: 27
  end

  def test() do
    a = %User{}
    IO.inspect a
    a = Map.put(a, :name, "change")
    IO.inspect a
  end

end

Test.test()

Answer 3

您可以尝试以下操作：

unit = %{
  __meta__: #Ecto.Schema.Metadata<:loaded, "units">,
  cdc_location_class_id: nil,
  description: "",
  facility: #Ecto.Association.NotLoaded<association :facility is not loaded>,
  facility_id: 2215,
  id: 719,
  is_active: true,
  name: "Unit",
  rooms: #Ecto.Association.NotLoaded<association :rooms is not loaded>
}

unit = case Ecto.assoc_loaded?(unit.facility) do
  false -> Map.put(unit, :facility, "not loaded")
  _ -> unit
end

用自定义值替换结构中的特定值

3 个答案: