How to render multiple relations using opts include

Questions / Help
1

Hi,
I am new to Elixir Phoenix and in the leaning process.

I am trying to implement the apis and have defined multiple schemas with belongs_to, has_one and has_many relations. Following is my controller function.

def show(conn, %{“id” => id}) do
state = GeoData.get_state!(id)
|> Repo.preload([:country, :cities])

# render(conn, "show.json-api", data: state, opts: [include: "cities, country"])
render(conn, "show.json-api", data: state, opts: [include: "country, cities"])

end

I want the GET on http://localhost:4000/api/states to return both country and cities info. However, this renders only cities or country, depending on the order in which I specify them in the render call above. How do I get the API to return both the relations or even more relations as applicable. Whats the syntax to render multiple such relations? Btw, I am able to successfully preload them before rendering and I verified the same with IO.inspect. Its just the rendering part thats failing.

Appreciate any help in this regard.

Thanks,
Rajasekhar.

2

Hello and welcome…

Then You should show your view show.json-api

Maybe also add this to your pipeline, and tell us what the state is

state = GeoData.get_state!(id)
|> Repo.preload([:country, :cities])
|> IO.inspect()

BTW I would not use that name for a view, I would prefer show-api.json… just to not mess with json type.

3

Hi, thanks for your response.

Here is the the output of IO.inspect. As we can see both cities and country are preloaded.

%MyApp.GeoData.State{
  __meta__: #Ecto.Schema.Metadata<:loaded, "states">,
  cities: [
    %MyApp.GeoData.City{
      __meta__: #Ecto.Schema.Metadata<:loaded, "cities">,
      id: 1,
      inserted_at: ~N[2020-07-15 15:31:45],
      is_hidden: false,
      name: "Lake Jaunita",
      state: #Ecto.Association.NotLoaded<association :state is not loaded>,
      state_id: 1,
      updated_at: ~N[2020-07-15 15:31:45]
    }
  ],
  country: %MyApp.GeoData.Country{
    __meta__: #Ecto.Schema.Metadata<:loaded, "countries">,
    id: 1,
    inserted_at: ~N[2020-07-15 15:31:45],
    is_hidden: false,
    name: "India",
    states: #Ecto.Association.NotLoaded<association :states is not loaded>,
    updated_at: ~N[2020-07-15 15:31:45]
  },
  country_id: 1,
  id: 1,
  inserted_at: ~N[2020-07-15 15:31:45],
  is_hidden: false,
  name: "South Dashawn",
  updated_at: ~N[2020-07-15 15:31:45]
}

And, my_app_web/views/state_view.ex file is as follows.

defmodule MyAppWeb.StateView do
  use MyAppWeb, :view
  use JaSerializer.PhoenixView
  attributes([:name, :is_hidden])
  has_one :country,
    serializer: MyAppWeb.CountryView,
    include: true,
    identifiers: :when_included
  has_many :cities,
    serializer: MyAppWeb.CityView,
    include: true,
    identifiers: :when_included
end

Regarding show.json-api, following was the recommendation given by Phoenix at the time of compilation after I switched to JaSerializer.

warning: Please use show.json-api instead. This will stop working in a future version.
warning: Passing data via `:model`, `:states` or `:state`
          atoms to JaSerializer.PhoenixView has be deprecated. Please use
          `:data` instead. This will stop working in a future version.
4

Please use code fence ``` to delimite your code… I edited your post to add them.

5

The problem is with the use of JaSerializer, but I cannot help You because I have never used it.

At least, your data seems fine :slight_smile:

6

@kokolegorille Thank you, appreciate your help so far.

Anybody else, who can help me to resolve this please? How to render data from multiple relationships in API?

7

Happy to share the issue is resolved. The issue is very trivial.

Referring to the documentation for includes option here(https://github.com/vt-elixir/ja_serializer),

Include

By specifying the include option, the serializer will only side-load the relationships specified. This option should be a comma separated list of relationships. Each relationship should be a dot separated path.
Example: include: "author,comments.author"

I somehow figured out that include options are comma separated, but there should not be any space in between. Once I removed the space between cities, and country, it started working.

Wrong stmt:  render(conn, "show.json-api", data: state, opts: [include: "cities, country"])
Correct stmt: render(conn, "show.json-api", data: state, opts: [include: "cities,country"])

It looks strange that white spaces are not handled and there is no explicit mention about this anywhere in the documentation. However, I am happy that issue is resolved.

Once again, thanks to @kokolegorille for your willingness to help.

1 Like
8

Here is what my API returns after the whitespace is removed in include options.
Data in json format that includes both cities and country info.

{
  "data": {
    "attributes": {
      "is-hidden": false,
      "name": "South Dashawn"
    },
    "id": "1",
    "relationships": {
      "cities": {
        "data": [
          {
            "id": "1",
            "type": "city"
          }
        ]
      },
      "country": {
        "data": {
          "id": "1",
          "type": "country"
        }
      }
    },
    "type": "state"
  },
  "included": [
    {
      "attributes": {
        "is-hidden": false,
        "name": "Lake Jaunita"
      },
      "id": "1",
      "type": "city"
    },
    {
      "attributes": {
        "is-hidden": false,
        "name": "India"
      },
      "id": "1",
      "type": "country"
    }
  ],
  "jsonapi": {
    "version": "1.0"
  }
}