Implement Access for form fields

Author: josevalim

lib/phoenix_html/form_field.ex

@@ -11,6 +11,8 @@ defmodule Phoenix.HTML.FormField do
     * `:name` - the `name` to be used as form input as a string
     * `:value` - the value for the input
 
+  This struct also implements the `Access` behaviour,
+  but raises if you try to access a field that is not defined.
   """
   @type t :: %__MODULE__{
           id: String.t(),
@@ -23,4 +25,21 @@ defmodule Phoenix.HTML.FormField do
 
   @enforce_keys [:id, :name, :errors, :field, :form, :value]
   defstruct [:id, :name, :errors, :field, :form, :value]
+
+  @behaviour Access
+
+  @impl true
+  def fetch(struct, key) do
+    {:ok, Map.fetch!(struct, key)}
+  end
+
+  @impl true
+  def get_and_update(struct, key, fun) do
+    Map.get_and_update!(struct, key, fun)
+  end
+
+  @impl true
+  def pop(struct, _key) do
+    raise ArgumentError, "cannot pop keys from #{inspect(struct)}"
+  end
 end

test/phoenix_html/form_test.exs

@@ -168,6 +168,9 @@ defmodule Phoenix.HTML.FormTest do
                name: "atom",
                errors: ["oops"]
              }
+
+      assert form[:key][:id] == "key"
+      assert form[:atom][:value] == "data"
     end
 
     test "with name and atom keys" do
@@ -193,6 +196,9 @@ defmodule Phoenix.HTML.FormTest do
                name: "search[atom]",
                errors: ["oops"]
              }
+
+      assert form[:key][:id] == "search_key"
+      assert form[:atom][:value] == "data"
     end
 
     test "without name and string keys" do
@@ -218,6 +224,9 @@ defmodule Phoenix.HTML.FormTest do
                name: "string",
                errors: ["oops"]
              }
+
+      assert form["key"][:id] == "key"
+      assert form["string"][:value] == "data"
     end
 
     test "with name and string keys" do
@@ -243,6 +252,9 @@ defmodule Phoenix.HTML.FormTest do
                name: "search[string]",
                errors: ["oops"]
              }
+
+      assert form["key"][:id] == "search_key"
+      assert form["string"][:value] == "data"
     end
   end