Jason.Encoder not implemented for %Geo.MultiPolygon. Better solution?

[cdesch]

Is there a better solution for this? I just had the `Jason.Encoder pipe to Poison, because I couldn't figure out how to get it to work otherwise. Here is my code:

lib/app_types.ex

Postgrex.Types.define(MyAppName.PostgresTypes,
              [Geo.PostGIS.Extension] ++ Ecto.Adapters.Postgres.extensions(),
              json: Jason)


defimpl Jason.Encoder, for: [Geo.MultiPolygon] do
  def encode(struct, opts) do
    Geo.JSON.encode!(struct) |> Poison.encode!
  end
end

config/config.exs

...
config :geo_postgis, json_library: Jason
...

config/dev.exs

config :my_app_name, MyAppName.Repo,
  username: "cj",
  #password: "postgres",
  database: "my_app_name_development",
  hostname: "localhost",
  show_sensitive_data_on_connection_error: true,
  pool_size: 10,
  types: MyAppName.PostgresTypes

lib/my_app_name/geo/fence.ex

defmodule MyAppName.Geo.Fence do
  use Ecto.Schema
  import Ecto.Changeset

  @derive {Jason.Encoder, only: [:geom]}
  schema "fences" do
    field :friendly_name, :string
    field :market_type, :string
    field :name, :string
    field :source_id, :string
    field :state, :string
    field :geoid, :string
    field :code, :string
    field :geom, Geo.PostGIS.Geometry

    timestamps()
  end

  @doc false
  def changeset(fence, attrs) do
    fence
    |> cast(attrs, [:name, :source_id, :market_type, :friendly_name, :state])
    |> validate_required([:name])
  end
end

[bryanjos]

You should be able to do:

defimpl Jason.Encoder, for: [Geo.MultiPolygon] do
  def encode(struct, opts) do
    Geo.JSON.encode!(struct) |> Jason.encode!
  end
end

The idea was to not be tied to a specific encoder. But now that most things have settled on Jason (or at least the Poison interface) we can make the JSON module here actually return json.

The json_library configuration item currently is used for when Ecto.Type.cast is used to turn the field into one of the geo structs if the field is a geojson string.

[josevalim]

If you want, you can also add Jason as an optional dependency, so you still don't impose it over users. :)

[s3cur3]

Ah! @josevalim, looks like this was solved in the geo package by #141 and made optional in #149. Taking version 3.3.6 or newer of Geo will resolve it. 😄