Merge pull request #124 from elixirkoans/protocols

Protocols

lib/koans/16_protocols.ex

@@ -0,0 +1,51 @@
+defmodule Protocols do
+  use Koans
+
+  @intro "Wan't to follow the rules? Adhere to the protocol!"
+
+  defprotocol School, do: def enrol(person)
+
+  defimpl School, for: Any do
+    def enrol(_) do
+      "Pupil enrolled at school"
+    end
+  end
+
+  defmodule Student do
+    @derive School
+    defstruct name: ""
+  end
+
+  defmodule Musician, do: defstruct name: "", instrument: ""
+  defmodule Dancer,  do: defstruct name: "", dance_style: ""
+  defmodule Baker, do: defstruct name: ""
+
+  defimpl School, for: Musician do
+    def enrol(musician) do
+      "#{musician.name} signed up for #{musician.instrument}"
+    end
+  end
+
+  defimpl School, for: Dancer do
+    def enrol(dancer), do: "#{dancer.name} enrolled for #{dancer.dance_style}"
+  end
+
+  koan "Sharing an interface is the secret at school" do
+    musician = %Musician{name: "Andre", instrument: "violin"}
+    dancer = %Dancer{name: "Darcy", dance_style: "ballet"}
+
+    assert School.enrol(musician) == ___
+    assert School.enrol(dancer) == ___
+  end
+
+  koan "Sometimes we all use the same" do
+    student = %Student{name: "Emily"}
+    assert School.enrol(student) == ___
+  end
+
+  koan "If you don't comply you can't get in" do
+    assert_raise ___, fn ->
+      School.enrol(%Baker{name: "Delia"})
+    end
+  end
+end

lib/runner.ex

@@ -16,6 +16,7 @@ defmodule Runner do
     Processes,
     Tasks,
     Agents,
+    Protocols,
   ]
 
   def koan?(koan), do: Enum.member?(@modules, koan)

mix.lock

@@ -1,2 +1,2 @@
-%{"exfswatch": {:hex, :exfswatch, "0.1.1"},
-  "fs": {:hex, :fs, "0.9.2"}}
+%{"exfswatch": {:hex, :exfswatch, "0.1.1", "7ccf6fc9b443d04dada3e50b21f910b4d0e4546ce7772dc6d4181fb929ea186f", [:mix], [{:fs, "~> 0.9", [hex: :fs, optional: false]}]},
+  "fs": {:hex, :fs, "0.9.2", "ed17036c26c3f70ac49781ed9220a50c36775c6ca2cf8182d123b6566e49ec59", [:rebar], []}}

test/koans/protocols_koans_test.exs

@@ -0,0 +1,14 @@
+defmodule ProtocolsTests do
+  use ExUnit.Case
+  import TestHarness
+
+  test "Protocols" do
+    answers = [
+      {:multiple, ["Andre signed up for violin", "Darcy enrolled for ballet"]},
+      "Pupil enrolled at school",
+      Protocol.UndefinedError
+    ]
+
+    test_all(Protocols, answers)
+  end
+end