add get_field function to adapter

lib/flop/adapter.ex

@@ -37,4 +37,6 @@ defmodule Flop.Adapter do
   @callback count(queryable, opts) :: non_neg_integer
 
   @callback list(queryable, opts) :: [any]
+
+  @callback get_field(any, atom, Flop.FieldInfo.t()) :: any
 end

lib/flop/adapter/ecto.ex

@@ -211,6 +211,26 @@ defmodule Flop.Adapter.Ecto do
     end)
   end
 
+  @impl Flop.Adapter
+  def get_field(%{} = item, _field, %FieldInfo{
+        extra: %{type: :compound, fields: fields}
+      }) do
+    Enum.map_join(fields, " ", &get_field(item, &1, %FieldInfo{}))
+  end
+
+  def get_field(%{} = item, _field, %FieldInfo{
+        extra: %{type: :join, path: path}
+      }) do
+    Enum.reduce(path, item, fn
+      field, %{} = acc -> Map.get(acc, field)
+      _, _ -> nil
+    end)
+  end
+
+  def get_field(%{} = item, field, %FieldInfo{}) do
+    Map.get(item, field)
+  end
+
   @impl Flop.Adapter
   def apply_filter(
         query,

lib/flop/schema.ex

@@ -895,7 +895,7 @@ defimpl Flop.Schema, for: Any do
     order_by_func =
       build_order_by_func(compound_fields, join_fields, alias_fields)
 
-    get_field_func = build_get_field_func(compound_fields, join_fields)
+    get_field_func = build_get_field_func(struct, adapter, adapter_opts)
 
     cursor_dynamic_func_compound =
       build_cursor_dynamic_func_compound(compound_fields)
@@ -1354,46 +1354,17 @@ defimpl Flop.Schema, for: Any do
     end
   end
 
-  def build_get_field_func(compound_fields, join_fields) do
-    compound_field_funcs =
-      for {name, fields} <- compound_fields do
-        quote do
-          def get_field(struct, unquote(name)) do
-            Enum.map_join(
-              unquote(fields),
-              " ",
-              &Flop.Schema.get_field(struct, &1)
-            )
-          end
-        end
-      end
-
-    join_field_funcs =
-      for {name, %{path: path}} <- join_fields do
-        quote do
-          def get_field(struct, unquote(name)) do
-            Enum.reduce(unquote(path), struct, fn field, acc ->
-              case acc do
-                %{} -> Map.get(acc, field)
-                _ -> nil
-              end
-            end)
-
-            # assoc = Map.get(struct, unquote(assoc_field)) || %{}
-            # Map.get(assoc, unquote(field))
-          end
-        end
-      end
-
-    fallback_func =
+  def build_get_field_func(struct, adapter, adapter_opts) do
+    for {field, field_info} <- adapter.fields(struct, adapter_opts) do
       quote do
-        def get_field(struct, field), do: Map.get(struct, field)
+        def get_field(struct, unquote(field)) do
+          unquote(adapter).get_field(
+            struct,
+            unquote(field),
+            unquote(Macro.escape(field_info))
+          )
+        end
       end
-
-    quote do
-      unquote(compound_field_funcs)
-      unquote(join_field_funcs)
-      unquote(fallback_func)
     end
   end