add nova

nova/src/Http/Controllers/FieldController.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Laravel\Nova\Http\Controllers;
+
+use Illuminate\Routing\Controller;
+use Laravel\Nova\Contracts\RelatableField;
+use Laravel\Nova\Http\Requests\NovaRequest;
+
+class FieldController extends Controller
+{
+    /**
+     * Retrieve the given field for the given resource.
+     *
+     * @param  \Laravel\Nova\Http\Requests\NovaRequest  $request
+     * @return \Illuminate\Http\JsonResponse
+     */
+    public function __invoke(NovaRequest $request)
+    {
+        $resource = $request->newResource();
+
+        $fields = $request->relatable
+                        ? $resource->availableFieldsOnIndexOrDetail($request)->whereInstanceOf(RelatableField::class)
+                        : $resource->availableFields($request);
+
+        return response()->json(
+            $fields->findFieldByAttribute($request->field, function () {
+                abort(404);
+            })
+        );
+    }
+}