JSON 将地理库中的 GEO.Point 编码为人类可读的形式

Question

我有这个架构，它有一个 Geo Geo.Point:

defmodule Api.Shop do
  use Ecto.Schema
  import Ecto.Changeset
  import Api.Repo
  import Ecto.Query

  @derive {Poison.Encoder, only: [:name, :place_id, :geo_json, :distance]}
  schema "shops" do
    field :name, :string
    field :place_id, :string
    field :point, Geo.Point
    field :geo_json, :string, virtual: true
    field :distance, :float, virtual: true

    timestamps()
  end

  def encode_model(shop) do
    %Api.Shop{shop | geo_json: Geo.JSON.encode(shop.point) }
  end

  defimpl Poison.Encoder, for: Api.Shop do
    def encode(shop, options) do
      shop = Api.Shop.encode_model(shop)
      Poison.Encoder.Map.encode(Map.take(shop, [:id, :name, :geo_json]), options)
    end
  end

  def changeset(shop, params \ %{}) do
    shop
    |> cast(params, [:name, :place_id, :point])
    |> validate_required([:name, :place_id, :point])
    |> unique_constraint(:place_id)
  end......
end

当我 return 查询中的 shop.point 字段时：

  def create_query_no_keyword(categories, shop_ids) do
    products_shops_categories = from p in Product,
    distinct: p.id,
    join: ps in ProductShop, on: p.id == ps.p_id,
    join: s in Shop, on: s.id == ps.s_id,
    join: pc in ProductCategory, on: p.id == pc.p_id,
    join: c in Subcategory, on: c.id == pc.c_id,
    where: c.id in ^categories,
    where: s.id in ^shop_ids,
    group_by: [p.id, p.name, p.brand],
    select: %{product: p, categories: fragment("json_agg( DISTINCT (?, ?)) AS category", c.id, c.name), shops: fragment("json_agg( DISTINCT (?, ?, ?)) AS shop", s.id, s.name, s.point)}
  end

得到 returned 的实际上是 0101000020E6100000A3BDB0EB0DD9654030AC2C1BE76D42C0，这是错误的格式 - WKB。我希望编码为具有可读坐标的 WKT。

如何让 s.point 成为 WKT 格式并因此具有坐标，当它被查询 return 编辑时？

Answer 1

我发现 this Stack Exchange GIS answer 是解决方案：

use this for point object:

SELECT ST_AsText(the_geom) 
       FROM myTable; and viewing X,Y and geom object:

SELECT ST_X(the_geom), ST_Y(the_geom), ST_AsText(the_geom) 
       FROM myTable;

Geo library is using PostGIS 和解决方案是特定于 PostGIS 的。您需要使用 ST_AsText 或来自 PostGIS 的 ST_X 和 ST_Y select 列。

我的 select 语句更改为：

select: %{product: p, categories: fragment("json_agg( DISTINCT (?, ?)) AS category", c.id, c.name), shops: fragment("json_agg( DISTINCT (?, ?, ST_X(?), ST_Y(?))) AS shop", s.id, s.name, s.point, s.point)}

JSON 将地理库中的 GEO.Point 编码为人类可读的形式

JSON encode GEO.Point from geo library as human readable form

ecto

geo

elixir

elixir-poison