Replace specific values in a struct with custom values

Question

I have different structs returned from database and i want to replace the value Ecto.Assoication.Notloaded with some custom value like not loaded in all of them.

This is one record

 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>
}

This is the map I want

 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"
}

Any suggestions?

Thanks

"Don't do it" would be my suggestion :) If you need to do it, you are probably doing something wrong. — denis.peplin
– denis.peplin, Commented Sep 4, 2018 at 10:20

Dogbert · Accepted Answer · 2018-09-04 17:39:17Z

1

I'd use :maps.map/2, pattern match on the value argument, and replace it as necessary:

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

If you need to run this on a list of maps, just put the above in a function and use Enum.map/2.

answered Sep 4, 2018 at 17:39

Dogbert

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1 Comment

Jonas Dellinger Over a year ago

You also could use the standard Enum.map function instead of :maps.map, couldn't you? But I guess you would have to add another Enum.into

chris · Accepted Answer · 2018-09-04 12:38:44Z

0

since structs are just maps, they work with the functions from the Map module

So you can use Map.put to replace the value. Here is the example:

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()

answered Sep 4, 2018 at 12:38

chris

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Comments

Lucas Franco · Accepted Answer · 2018-09-04 12:44:12Z

0

You can try something like this:

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

answered Sep 4, 2018 at 12:44

Lucas Franco

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