After 'mix phx.gen.json Items Item items name:string description:string info:string amount:integer factor:float type:string --no-context --no-schema'.

lib/generic_rest_server_web/controllers/item_json.ex

@@ -0,0 +1,29 @@
+defmodule GenericRestServerWeb.ItemJSON do
+  alias GenericRestServer.Items.Item
+
+  @doc """
+  Renders a list of items.
+  """
+  def index(%{items: items}) do
+    %{data: for(item <- items, do: data(item))}
+  end
+
+  @doc """
+  Renders a single item.
+  """
+  def show(%{item: item}) do
+    %{data: data(item)}
+  end
+
+  defp data(%Item{} = item) do
+    %{
+      id: item.id,
+      name: item.name,
+      description: item.description,
+      info: item.info,
+      amount: item.amount,
+      factor: item.factor,
+      type: item.type
+    }
+  end
+end