返回列表会给(Poison.EncodeError)无法编码值

Question

IO.puts(inspect(contacts))给出:

 [%HelloTable.Contact{__meta__: #Ecto.Schema.Metadata<:loaded>, 
 id: 37,   
 inserted_at: #Ecto.DateTime<2015-10-22T12:50:43Z>, 
 name: "Gumbo", phone: "(801) 555-55555", 
 updated_at: #Ecto.DateTime<2015-10-22T12:50:43Z>}]

视图看起来像:

defmodule HelloTable.ContactView do
  use HelloTable.Web, :view

  def render("index.json", %{contacts: contacts}) do
    IO.puts(inspect( contacts ))
    contacts
  end

end

一旦我尝试渲染这个视图,我得到:

** (Poison.EncodeError) unable to encode value: {nil, "contacts"}

Answer 1

您需要实现Poison.Encoder协议,HelloTable.Contact如在elixir中将Ecto模型编码为JSON中所述,或者使用render_many/4从渲染函数返回一个映射:

defmodule HelloTable.ContactView do
  use HelloTable.Web, :view

  def render("index.json", %{contacts: contacts}) do
    render_many(contacts, __MODULE__, "contact.json")
  end

  def render("contact.json", %{contact: contact}) do
    %{
      id: contact.id,
      name: contact.name,
      phone_number: contact.phone
    }
  end    
end

以上是在Phoenix JSON生成器中处理JSON的方法.