Merge pull request #28 from ukutaht/structs

Basic Koans about structs

lib/koans/08_structs.ex

@@ -0,0 +1,59 @@
+defmodule Structs do
+  use Koans
+
+  defmodule Person do
+    defstruct [:name, :age ]
+  end
+
+  koan "structs are defined and named after a module" do
+    assert %Person{}
+  end
+
+  koan "you can access the fields of a struct" do
+    nobody = %Person{}
+    assert nobody.age == nil
+    assert nobody.name == nil
+  end
+
+  koan "You can pass initial values to structs" do
+    joe = %Person{name: "Joe", age: 23}
+    assert joe.age == 23
+    assert joe.name == "Joe"
+  end
+
+  koan "update fields with the pipe '|' operator" do
+    joe = %Person{name: "Joe", age: 23}
+    older = %{ joe | age: joe.age + 10}
+    assert  older.age == 33
+  end
+
+  koan "the original struct is not affected by updates" do
+    joe = %Person{name: "Joe", age: 23}
+    assert %{ joe | age: joe.age + 10}.age == 33
+    assert joe.age == 23
+  end
+
+  koan "you can pattern match into the fields of a struct" do
+    %Person{age: age} = %Person{age: 22, name: "Silvia"}
+    assert age == 22
+  end
+
+  defmodule Plane do
+    defstruct passengers: 0, maker: :boeing
+  end
+
+  koan "or onto the type of the struct itself" do
+    assert is_a_plane(%Plane{passengers: 417, maker: :boeing})
+    refute is_a_plane(%Person{age: 22, name: "Silvia"})
+  end
+
+  def is_a_plane(%Plane{}), do: true
+  def is_a_plane(_), do: false
+
+  koan "are basically maps" do
+    silvia = %Person{age: 22, name: "Silvia"}
+
+    assert is_map(silvia)
+    assert Map.fetch!(silvia, :age) == 22
+  end
+end

lib/runner.ex

@@ -6,7 +6,8 @@ defmodule Runner do
     Maps,
     Functions,
     Enums,
-    Arithmetic
+    Arithmetic,
+    Structs
   ]
 
   def run(options) do

lib/watcher.ex

@@ -4,7 +4,7 @@ defmodule Watcher do
   def callback(file, events)  do
     if Enum.member?(events, :modified) do
       try do
-        [{mod, _}] = Code.load_file(file)
+        [{mod, _} | _] = Code.load_file(file)
         Runner.run(mod)
       rescue
         e -> Display.format_compile_error(e)