From https://once.com/writebook

app/controllers/pictures_controller.rb

@@ -0,0 +1,10 @@
+class PicturesController < LeafablesController
+  private
+    def new_leafable
+      Picture.new leafable_params
+    end
+
+    def leafable_params
+      params.fetch(:picture, {}).permit(:image, :caption)
+    end
+end