support using anonymous function to customize relational queries.

framework/db/ar/ActiveFinder.php

@@ -234,7 +234,7 @@ class ActiveFinder extends \yii\base\Object
 	/**
 	 * @param JoinElement $parent
 	 * @param array|string $with
-	 * @param array $config
+	 * @param array|\Closure $config
 	 * @return null|JoinElement
 	 * @throws \yii\db\Exception
 	 */

framework/db/ar/ActiveRecord.php

@@ -555,7 +555,7 @@ abstract class ActiveRecord extends Model
 	 * If the relation is HAS_MANY or MANY_MANY, it will return an array of objects
 	 * or an empty array.
 	 * @param ActiveRelation|string $relation the relation object or the name of the relation
-	 * @param array $params additional parameters that customize the query conditions as specified in the relation declaration.
+	 * @param array|\Closure $params additional parameters that customize the query conditions as specified in the relation declaration.
 	 * @return mixed the related object(s).
 	 * @throws Exception if the relation is not specified in [[relations()]].
 	 */
@@ -569,8 +569,12 @@ abstract class ActiveRecord extends Model
 			$relation = $md->relations[$relation];
 		}
 		$relation = clone $relation;
-		foreach ($params as $name => $value) {
-			$relation->$name = $value;
+		if ($params instanceof \Closure) {
+			call_user_func($params, $relation);
+		} else {
+			foreach ($params as $name => $value) {
+				$relation->$name = $value;
+			}
 		}
 
 		$finder = new ActiveFinder($this->getDbConnection());

tests/unit/framework/db/ar/ActiveRecordTest.php

@@ -258,6 +258,14 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		// has many and base limited
 		$orders = Order::find()->with('items')->order('@.id')->limit(2)->all();
 		$this->assertEquals(2, count($orders));
+		$this->assertEquals(1, $orders[0]->items[0]->id);
+
+		/// customize "with" query
+		$orders = Order::find()->with(array('items' => function($q) {
+			$q->order('@.id DESC');
+		}))->order('@.id')->limit(2)->all();
+		$this->assertEquals(2, count($orders));
+		$this->assertEquals(2, $orders[0]->items[0]->id);
 
 		// findBySql with
 		$orders = Order::findBySql('SELECT * FROM tbl_order WHERE customer_id=2')->with('items')->all();
@@ -314,11 +322,13 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		));
 		$this->assertEquals(1, count($orders));
 		$this->assertEquals(3, $orders[0]->id);
+
 		// original results are kept after customized query
 		$orders = $customer->orders;
 		$this->assertEquals(2, count($orders));
 		$this->assertEquals(2, $orders[0]->id);
 		$this->assertEquals(3, $orders[1]->id);
+
 		// as array
 		$orders = $customer->orders(array(
 			'asArray' => true,
@@ -327,5 +337,14 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		$this->assertTrue(is_array($orders[0]));
 		$this->assertEquals(2, $orders[0]['id']);
 		$this->assertEquals(3, $orders[1]['id']);
+
+		// using anonymous function to customize query condition
+		$orders = $customer->orders(function($q) {
+			$q->order('@.id DESC')->asArray();
+		});
+		$this->assertEquals(2, count($orders));
+		$this->assertTrue(is_array($orders[0]));
+		$this->assertEquals(3, $orders[0]['id']);
+		$this->assertEquals(2, $orders[1]['id']);
 	}
 }
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