first commit

core/modules/file/src/ComputedFileUrl.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Drupal\file;
+
+use Drupal\Core\TypedData\TypedData;
+
+/**
+ * Computed file URL property class.
+ */
+class ComputedFileUrl extends TypedData {
+
+  /**
+   * Computed root-relative file URL.
+   *
+   * @var string
+   */
+  protected $url = NULL;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getValue() {
+    if ($this->url !== NULL) {
+      return $this->url;
+    }
+
+    assert($this->getParent()->getEntity() instanceof FileInterface);
+
+    $uri = $this->getParent()->getEntity()->getFileUri();
+    /** @var \Drupal\Core\File\FileUrlGeneratorInterface $file_url_generator */
+    $file_url_generator = \Drupal::service('file_url_generator');
+    $this->url = $file_url_generator->generateString($uri);
+
+    return $this->url;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setValue($value, $notify = TRUE) {
+    $this->url = $value;
+
+    // Notify the parent of any changes.
+    if ($notify && isset($this->parent)) {
+      $this->parent->onChange($this->name);
+    }
+  }
+
+}