Exqlite.TypeExtensions

Runtime extensions to convert data types into something that can be
serialized into the database.

Author: aseigo

README.md

@@ -46,12 +46,17 @@ end
 ### Runtime Configuration
 
 ```elixir
-config :exqlite, default_chunk_size: 100
+config :exqlite,
+    default_chunk_size: 100,
+    type_extensions: [MyApp.TypeExtension]
 ```
 
 * `default_chunk_size` - The chunk size that is used when multi-stepping when
   not specifying the chunk size explicitly.
-  
+* `type_extensions`: An optional list of modules that implement the
+  Exqlite.TypeExtension behaviour, allowing types beyond the default set that
+  can be stored and retrieved from the database.
+
 ### Compile-time Configuration
 
 In `config/config.exs`,

lib/exqlite/extension.ex

@@ -0,0 +1,11 @@
+defmodule Exqlite.TypeExtension do
+  @moduledoc """
+  A behaviour that defines the API for extensions providing custom data loaders and dumpers
+  for Ecto schemas.
+  """
+
+  @doc """
+  Takes a value and convers it to data suitable for storage in the database.
+  """
+  @callback convert(value :: term) :: term
+end

lib/exqlite/sqlite3.ex

@@ -481,5 +481,20 @@ defmodule Exqlite.Sqlite3 do
     raise ArgumentError, "#{inspect(datetime)} is not in UTC"
   end
 
-  defp convert(val), do: val
+  defp convert(val) do
+    convert_with_type_extensions(type_extensions(), val)
+  end
+
+  defp convert_with_type_extensions([], val), do: val
+
+  defp convert_with_type_extensions([extension | other_extensions], val) do
+    case extension.convert(val) do
+      nil -> convert_with_type_extensions(other_extensions, val)
+      convert -> convert
+    end
+  end
+
+  defp type_extensions() do
+    Application.get_env(:exqlite, :type_extensions, [])
+  end
 end