Add preProcessIndex method to field type

Author: esdoefom

src/Fieldtypes/CurrencyFieldtype.php

@@ -31,9 +31,9 @@ public function defaultValue()
      * Pre-process the data before it gets sent to the publish page.
      *
      * @param mixed $data
-     * @return array|mixed
+     * @return string|null
      */
-    public function preProcess($data)
+    public function preProcess($data): ?string
     {
         if ($data === null) {
             return null;
@@ -46,6 +46,22 @@ public function preProcess($data)
         return trim(str_replace($symbol, '', $formatted));
     }
 
+    /**
+     * Pre-process the data before it gets sent to the publish page.
+     *
+     * @param $data
+     * @return string|null
+     */
+    public function preProcessIndex($data): ?string
+    {
+        if ($data === null) {
+            return null;
+        }
+
+        $fmt = App::make(NumberFormatter::class, ['iso' => $this->getIso()]);
+        return $fmt->formatCurrency($data, $this->getIso());
+    }
+
     /**
      * Process the data before it gets saved.
      *