Issue #1720784 by Berdir: Add method for getting an entity's UUID.

core/modules/entity/lib/Drupal/entity/Entity.php

@@ -65,6 +65,13 @@ class Entity implements EntityInterface {
     return isset($this->id) ? $this->id : NULL;
   }
 
+  /**
+   * Implements EntityInterface::uuid().
+   */
+  public function uuid() {
+    return isset($this->uuid) ? $this->uuid : NULL;
+  }
+
   /**
    * Implements EntityInterface::isNew().
    */

core/modules/entity/lib/Drupal/entity/EntityInterface.php

@@ -32,6 +32,17 @@ interface EntityInterface {
    */
   public function id();
 
+  /**
+   * Returns the entity UUID (Universally Unique Identifier).
+   *
+   * The UUID is guaranteed to be unique and can be used to identify an entity
+   * across multiple systems.
+   *
+   * @return string
+   *   The UUID of the entity, or NULL if the entity does not have one.
+   */
+  public function uuid();
+
   /**
    * Returns whether the entity is new.
    *

core/modules/entity/lib/Drupal/entity/Tests/EntityUUIDTest.php

@@ -41,35 +41,35 @@ class EntityUUIDTest extends WebTestBase {
       'name' => $this->randomName(),
       'uuid' => $uuid,
     ));
-    $this->assertIdentical($custom_entity->get('uuid'), $uuid);
+    $this->assertIdentical($custom_entity->uuid(), $uuid);
     // Save this entity, so we have more than one later.
     $custom_entity->save();
 
     // Verify that a new UUID is generated upon creating an entity.
     $entity = entity_create('entity_test', array('name' => $this->randomName()));
-    $uuid = $entity->get('uuid');
+    $uuid = $entity->uuid();
     $this->assertTrue($uuid);
 
     // Verify that the new UUID is different.
-    $this->assertNotEqual($custom_entity->get('uuid'), $uuid);
+    $this->assertNotEqual($custom_entity->uuid(), $uuid);
 
     // Verify that the UUID is retained upon saving.
     $entity->save();
-    $this->assertIdentical($entity->get('uuid'), $uuid);
+    $this->assertIdentical($entity->uuid(), $uuid);
 
     // Verify that the UUID is retained upon loading.
     $entity_loaded = entity_test_load($entity->id(), TRUE);
-    $this->assertIdentical($entity_loaded->get('uuid'), $uuid);
+    $this->assertIdentical($entity_loaded->uuid(), $uuid);
 
     // Verify that entity_load_by_uuid() loads the same entity.
     $entity_loaded_by_uuid = entity_load_by_uuid('entity_test', $uuid, TRUE);
-    $this->assertIdentical($entity_loaded_by_uuid->get('uuid'), $uuid);
+    $this->assertIdentical($entity_loaded_by_uuid->uuid(), $uuid);
     $this->assertEqual($entity_loaded_by_uuid, $entity_loaded);
 
     // Creating a duplicate needs to result in a new UUID.
     $entity_duplicate = $entity->createDuplicate();
-    $this->assertNotEqual($entity_duplicate->get('uuid'), $entity->get('uuid'));
-    $this->assertNotNull($entity_duplicate->get('uuid'));
+    $this->assertNotEqual($entity_duplicate->uuid(), $entity->uuid());
+    $this->assertNotNull($entity_duplicate->uuid());
     $entity_duplicate->save();
     $this->assertNotEqual($entity->id(), $entity_duplicate->id());
   }