Add the possibility to decode lists of items with deftype (#601)

lib/trento/support/type.ex

@@ -100,6 +100,19 @@ defmodule Trento.Type do
       def cast_and_validate_required_embed(changeset, field, required_fields),
         do: cast_embed(changeset, field, required: field in required_fields)
 
+      def from_list(list_of_structs) do
+        list_of_structs
+        |> Enum.map(fn item -> __MODULE__.new(item) end)
+        |> Enum.group_by(
+          fn {is_valid, _} -> is_valid end,
+          fn {_, decoding_value} -> decoding_value end
+        )
+        |> decoding_results()
+      end
+
+      defp decoding_results(%{error: decoding_errors}), do: {:error, decoding_errors}
+      defp decoding_results(%{ok: decoding_results}), do: {:ok, decoding_results}
+
       defp fields, do: __MODULE__.__schema__(:fields) -- __MODULE__.__schema__(:embeds)
 
       defp embedded_fields, do: __MODULE__.__schema__(:embeds)

test/trento/support/type_test.exs

@@ -33,4 +33,56 @@ defmodule Trento.TypeTest do
                name: "a"
              })
   end
+
+  test "should validate a list of maps" do
+    assert {:error, [%{embedded: ["can't be blank"]}, %{embedded: ["can't be blank"]}]} ==
+             TestData.from_list([
+               %{id: Faker.UUID.v4(), name: "carbonara"},
+               %{id: Faker.UUID.v4(), name: "amatriciana"}
+             ])
+
+    assert {:error, [%{embedded: ["can't be blank"]}, %{embedded: ["can't be blank"]}]} ==
+             TestData.from_list([
+               %{id: Faker.UUID.v4(), name: "carbonara"},
+               %{id: Faker.UUID.v4(), name: "amatriciana"},
+               %{
+                 id: Faker.UUID.v4(),
+                 name: "cacio_pepe",
+                 embedded: %{id: Faker.UUID.v4(), name: "yay"}
+               }
+             ])
+
+    {
+      :ok,
+      [
+        %TestData{
+          embedded: %EmbeddedTestData{id: _id1, name: "yay"},
+          id: _id2,
+          name: "cacio_pepe"
+        },
+        %TestData{
+          embedded: %EmbeddedTestData{
+            id: _id3,
+            name: "wow"
+          },
+          id: _id4,
+          name: "lasagne"
+        }
+      ] = decoded_list
+    } =
+      TestData.from_list([
+        %{
+          id: Faker.UUID.v4(),
+          name: "cacio_pepe",
+          embedded: %{id: Faker.UUID.v4(), name: "yay"}
+        },
+        %{
+          id: Faker.UUID.v4(),
+          name: "lasagne",
+          embedded: %{id: Faker.UUID.v4(), name: "wow"}
+        }
+      ])
+
+    assert 2 == length(decoded_list)
+  end
 end