菲尼克斯JSON加入和预加载数据

我想呈现与两个模型（事件和活动）跨越foreign_key相关的JSON。菲尼克斯JSON加入和预加载数据

在控制器，我执行这个查询：

def all_nested(conn, %{"event_id" => id}) do 
    event = Repo.get! nested_all_query, id 
    render(conn, "show_all.json", event: event) 
end 

defp nested_all_query do 
    from event in Event, 
    left_join: activities in assoc(event, :activities), 
    preload: [activities: activities] 
end

当我尝试IEX控制台上查询，查询返回正确的结果，它具有活动的“活动”数组中。

然后，渲染的时候，我有鉴于这样的代码：

def render("show_all.json", %{event: event}) do 
    render_one(event, Project.EventView, "event_all.json") 
end 

def render("event.json", %{event: event}) do 
    %{id: event.id, 
    name: event.name, 
    description: event.description, 
    num_participants: event.num_participants, 
    minimum_age: event.minimum_age, 
    price: event.price, 
    date_start: event.date_start, 
    date_end: event.date_end, 
    reg_date_open: event.reg_date_open, 
    reg_date_close: event.reg_date_close, 
    rules: event.rules} 
end 

def render("event_all.json", %{event: event}) do 
    render("event.json", %{event: event}) 
    |> Map.put_new(:activities, render_many(event.activities, Project.ActivityView, "activity.json")) 
end

我打电话render_many的活动得到ActivityView渲染渲染动作（单独为这个动作正常工作）JSON。

有了这个代码，我有这样的错误：

[error] #PID<0.575.0> running Project.Endpoint terminated 
Server: localhost:4000 (http) 
Request: GET /api/events/1/all 
** (exit) an exception was raised: 
    ** (Poison.EncodeError) unable to encode value: {nil, "activities"} 
     (poison) lib/poison/encoder.ex:354: Poison.Encoder.Any.encode/2 
     (poison) lib/poison/encoder.ex:213: anonymous fn/4 in Poison.Encoder.Map.encode/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map."-encode/3-lists^foldl/2-0-"/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map.encode/3 
     (poison) lib/poison/encoder.ex:213: anonymous fn/4 in Poison.Encoder.Map.encode/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map."-encode/3-lists^foldl/2-0-"/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map.encode/3 
     (poison) lib/poison/encoder.ex:232: anonymous fn/3 in Poison.Encoder.List.encode/3 
     (poison) lib/poison/encoder.ex:233: Poison.Encoder.List."-encode/3-lists^foldr/2-1-"/3 
     (poison) lib/poison/encoder.ex:233: Poison.Encoder.List.encode/3 
     (poison) lib/poison/encoder.ex:213: anonymous fn/4 in Poison.Encoder.Map.encode/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map."-encode/3-lists^foldl/2-0-"/3 
     (poison) lib/poison/encoder.ex:214: Poison.Encoder.Map.encode/3 
     (poison) lib/poison.ex:41: Poison.encode!/2 
     (phoenix) lib/phoenix/controller.ex:642: Phoenix.Controller.do_render/4 
     (project) web/controllers/event_controller.ex:1: Project.EventController.action/2 
     (project) web/controllers/event_controller.ex:1: Project.EventController.phoenix_controller_pipeline/2 
     (project) lib/project/endpoint.ex:1: Project.Endpoint.instrument/4 
     (project) lib/phoenix/router.ex:261: Project.Router.dispatch/2 
     (project) web/router.ex:1: Project.Router.do_call/2

我在做什么错？

问候

来源

2016-11-28 Mou

解决增加为：活动render_many这样的：

def render("event_all.json", %{event: event}) do 
    render("event.json", %{event: event}) 
    |> Map.put_new(:activities, render_many(event.activities, Project.ActivityView, "activity.json", as: :activity)) 
end

来源

2016-11-28 17:45:51 Mou

菲尼克斯JSON加入和预加载数据

回答

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