🚀 Load country data on compile time

lib/countries.ex

@@ -22,32 +22,41 @@ defmodule Countries do
       country[attribute] == value_as_char_list
     end)
   end
-
-  defp countries do
-    # Lets load all country data from our yaml files
-    codes = List.first(:yamerl.decode_file(data_path "countries.yaml"))
-    country_data =
-      Enum.reduce(codes, [], fn (code, countries) ->
-        countries ++ :yamerl.decode_file(data_path "countries/#{code}.yaml")
-      end)
-
-    # :yamerl returns a really terrible data structure
-    #    [[{'name', 'Germany'}, {'code', 'DE'}], [{'nam:e', 'Austria'}, {'code', 'AT'}]]
-    # We need to transform that to maps:
-    #    [%{name: 'Germany', code: "DE"}, %{name: 'Austria', code: "AT"}]
-    countries =
-      Enum.reduce(country_data, [], fn (country_data, countries) ->
-        country =
-          Enum.reduce(country_data, %Country{}, fn({key, value}, country) ->
-            key_as_atom = String.to_atom(to_string key)
-            Map.put(country, key_as_atom, value)
-          end)
-
-        List.insert_at(countries, 0, country)
-      end)
-  end
-
-  defp data_path(path) do
+
+  #-- Load countries from yaml files once on compile time ---
+
+  # Ensure :yamerl is running
+  Application.ensure_all_started(:yamerl)
+
+  data_path = fn(path) ->
     Path.join("data", path) |> Path.expand(__DIR__)
   end
+
+  # Lets load all country data from our yaml files
+  codes = List.first(:yamerl.decode_file data_path.("/countries.yaml"))
+  country_data =
+    Enum.reduce(codes, [], fn (code, countries) ->
+      countries ++ :yamerl.decode_file data_path.("countries/#{code}.yaml")
+    end)
+
+  # :yamerl returns a really terrible data structure
+  #    [[{'name', 'Germany'}, {'code', 'DE'}], [{'nam:e', 'Austria'}, {'code', 'AT'}]]
+  # We need to transform that to maps:
+  #    [%{name: 'Germany', code: "DE"}, %{name: 'Austria', code: "AT"}]
+  countries =
+    Enum.reduce(country_data, [], fn (country_data, countries) ->
+      country =
+        Enum.reduce(country_data, %Country{}, fn({attribute, value}, country) ->
+          attribute_as_atom = String.to_atom(to_string attribute)
+          Map.put(country, attribute_as_atom, value)
+        end)
+
+      List.insert_at(countries, 0, country)
+    end)
+
+  defp countries do
+    # Maps and Structs need to be escaped before unquoting
+    unquote Macro.escape(countries)
+  end
+
 end