returning a list gives (Poison.EncodeError) unable to encode value

Question

IO.puts(inspect( contacts )) gives:

 [%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>}]

And the view looks like:

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

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

end

As soon as I try to render this view I get:

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

Answer 1

You will need to either implement the Poison.Encoder protocol for HelloTable.Contact as described in Encoding a Ecto Model to JSON in elixir or return a map from the render function using render_many/4:

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

The above is how JSON is handled with in the Phoenix JSON generators.