jeromedoyle

JSON API response to Structs using Ecto Schema

Does anyone have an example of using Ecto Schemas for parsing JSON api responses?
I’m curious how you can convert this

{
    "id": 283230,
    "fname": "John",
    "lname": "Smith",
    "email": "john.smith@example.com",
    "createdOn": "2016-03-31T10:49:11.386-05:00",
    "updatedOn": "2016-10-31T16:36:12.968-05:00",
    "_embedded": {
      "addresses": [
        {
          "city": "Minneapolis",
          "state": "MN"
        },
        {
          "city": "New Orleans",
          "state": "LA"
        }
      ]
    }
}

into this

%User{
  id: 283230,
  fname: "John",
  lname: "Smith",
  email: "john.smith@example.com",
  createdOn: "2016-03-31T10:49:11.386-05:00",
  updatedOn: "2016-10-31T16:36:12.968-05:00",
  addresses: [
    %Address{
      "city": "Minneapolis",
      "state": "MN"
    },
    %Address{
      "city": "New Orleans",
      "state": "LA"
    }
  ]
}

6 comments

#ecto #api #json

0 3682 6

2021-09-18 20:07:22 UTC

First Post!

NobbZ

Poison and its protocols are designed for this.

There might be alternatives available, but poison is in phoenix by default.

Post #2

Most Liked

IvanR

One alternative valid way is to use Jason and plain structs with @type t :: ... definitions plus Domo for validation.

Considering MapShaper module from this example app, the structs can be defined like:

defmodule Address do
  @moduledoc false

  use Domo

  defstruct [city: "", state: ""]

  @type t :: %__MODULE__{city: String.t(), state: String.t()}
end

defmodule User do
  @moduledoc false

  use Domo

  today = NaiveDateTime.utc_now()
  defstruct [id: 0, fname: "", lname: "", email: "", createdOn: today, updatedOn: today, addresses: [%Address{}]]

  @type t :: %__MODULE__{
    id: non_neg_integer(),
    fname: String.t(),
    lname: String.t(),
    email: String.t(),
    createdOn: NaiveDateTime.t(),
    updatedOn: NaiveDateTime.t(),
    addresses: [Address.t()]
  }

  defimpl MapShaper.Target do
    def translate_source_map(_value, map) do
      addresses = get_in(map, ["_embedded", "addresses"])
      created_on = map |> get_in(["createdOn"]) |> parse_date()
      updated_on = map |> get_in(["updatedOn"]) |> parse_date()

      map
      |> Map.put("addresses", addresses)
      |> Map.put("createdOn", created_on)
      |> Map.put("updatedOn", updated_on)
    end

    defp parse_date(str) do
      str
      |> NaiveDateTime.from_iso8601()
      |> then(fn
        {:ok, date_time} -> date_time
        _ -> nil
      end)
    end
  end
end

And parsing + validation that looks like:

with {:ok, binary} <- File.read("user.json"),
      {:ok, map} <- Jason.decode(binary),
      user = MapShaper.from_map(%User{}, map),
      {:ok, user} <- User.ensure_type_ok(user) do
  user
end

Returns the following nested struct for the valid input:

%User{
  id: 283230,
  fname: "John",
  lname: "Smith",
  email: "john.smith@example.com",
  createdOn: ~N[2016-03-31 10:49:11.386],
  updatedOn: ~N[2016-10-31 16:36:12.968],
  addresses: [
    %Address{city: "Minneapolis", state: "MN"},
    %Address{city: "New Orleans", state: "LA"}
  ]
}

Post #7