Fixes #439

src/Jenssegers/Mongodb/Relations/BelongsToMany.php

@@ -104,7 +104,7 @@ class BelongsToMany extends EloquentBelongsToMany {
 
 		$records = $this->formatSyncList($ids);
 
-		$detach = array_diff($current, array_keys($records));
+		$detach = array_values(array_diff($current, array_keys($records)));
 
 		// Next, we will take the differences of the currents and given IDs and detach
 		// all of the entities that exist in the "current" array but are not in the
@@ -159,31 +159,28 @@ class BelongsToMany extends EloquentBelongsToMany {
 			$model = $id; $id = $model->getKey();
 		}
 
-		$records = $this->createAttachRecords((array) $id, $attributes);
-
-		// Get the ids to attach to the parent and related model.
-		$otherIds = array_pluck($records, $this->otherKey);
-		$foreignIds = array_pluck($records, $this->foreignKey);
+		$ids = (array) $id;
 
 		// Attach the new ids to the parent model.
-		$this->parent->push($this->otherKey, $otherIds, true);
+		$this->parent->push($this->otherKey, $ids, true);
 
-		// If we have a model instance, we can psuh the ids to that model,
+		// If we have a model instance, we can push the ids to that model,
 		// so that the internal attributes are updated as well. Otherwise,
 		// we will just perform a regular database query.
 		if (isset($model))
 		{
 			// Attach the new ids to the related model.
-			$model->push($this->foreignKey, $foreignIds, true);
+			$model->push($this->foreignKey, $this->parent->getKey(), true);
 		}
 		else
 		{
 			$query = $this->newRelatedQuery();
 
-			$query->where($this->related->getKeyName(), $id);
+			// Select related models.
+			$query->whereIn($this->related->getKeyName(), $ids);
 
-			// Attach the new ids to the related model.
-			$query->push($this->foreignKey, $foreignIds, true);
+			// Attach the new parent id to the related model.
+			$query->push($this->foreignKey, $this->parent->getKey(), true);
 		}
 
 		if ($touch) $this->touchIfTouching();

tests/RelationsTest.php

@@ -277,6 +277,34 @@ class RelationsTest extends TestCase {
         $this->assertCount(1, $user->clients);
     }
 
+    public function testBelongsToManyAttachArray()
+    {
+        $user = User::create(array('name' => 'John Doe'));
+        $client1 = Client::create(array('name' => 'Test 1'))->_id;
+        $client2 = Client::create(array('name' => 'Test 2'))->_id;
+
+        $user = User::where('name', '=', 'John Doe')->first();
+        $user->clients()->attach([$client1, $client2]);
+        $this->assertCount(2, $user->clients);
+    }
+
+    public function testBelongsToManySyncAlreadyPresent()
+    {
+        $user = User::create(array('name' => 'John Doe'));
+        $client1 = Client::create(array('name' => 'Test 1'))->_id;
+        $client2 = Client::create(array('name' => 'Test 2'))->_id;
+
+        $user->clients()->sync([$client1, $client2]);
+        $this->assertCount(2, $user->clients);
+
+        $user = User::where('name', '=', 'John Doe')->first();
+        $user->clients()->sync([$client1]);
+        $this->assertCount(1, $user->clients);
+
+        $user = User::where('name', '=', 'John Doe')->first()->toArray();
+        $this->assertCount(1, $user['client_ids']);
+    }
+
     public function testBelongsToManyCustom()
     {
         $user = User::create(array('name' => 'John Doe'));