Protocol examples updated to use Structs

lib/koans/16_protocols.ex

@@ -0,0 +1,50 @@
+defmodule Protocols do
+  use Koans
+
+  defprotocol School do
+    def enrol(person)
+  end
+
+  defmodule Student do
+    defstruct name: ""
+  end
+
+  defmodule Dancer do
+    defstruct name: "", dance_style: ""
+  end
+
+  defmodule Baker do
+    defstruct name: ""
+  end
+
+  defimpl School, for: Student do
+    def enrol(student) do
+      "#{student.name} enrolled at secondary school"
+    end
+  end
+
+  defimpl School, for: Dancer do
+    def enrol(dancer) do
+      "#{dancer.name} enrolled for #{dancer.dance_style}"
+    end
+  end
+
+  defmodule EveningSchool do end
+
+  koan "Sharing an interface is the secret at school" do
+    student = %Student{name: "Emily"}
+    assert School.enrol(student) == ___
+  end
+
+  koan "Dancers share but belong to a different school" do
+    dancer = %Dancer{name: "Darcy", dance_style: "ballet"}
+    assert School.enrol(dancer) == ___
+
+  end
+
+  koan "If you don't comply you can't get in" do
+    assert_raise ___, fn ->
+      School.enrol(%Baker{name: "Delia"})
+    end
+  end
+end