src/Interfaces/PersistentData/IPersistentDataManager.php

@@ -16,6 +16,8 @@ interface IPersistentDataManager
 
     public function loadRelationsFromDb(Model $model, bool $recursive = false, array $withRelations = []): void;
 
+    public function loadMultiRelationsFromDb(array $models, string $relation, bool $useRelations = false, array $withRelations = []): void;
+
     public function saveToDb(Model $model): void;
 
     public function deleteFromDb(Model $model): void;

src/PersistentData/Model/Model.php

@@ -8,6 +8,8 @@ abstract class Model
 
     protected static array $relations = [];
 
+    protected static array $multiRelations = [];
+
     protected $id = null;
 
     private array $snapshot = [];
@@ -27,6 +29,11 @@ abstract class Model
         return static::$relations;
     }
 
+    public static function getMultiRelations(): array
+    {
+        return static::$multiRelations;
+    }
+
     public function setId($id): void
     {
         $this->id = $id;

src/PersistentData/PersistentDataManager.php

@@ -92,6 +92,40 @@ class PersistentDataManager implements IPersistentDataManager
         }
     }
 
+    public function loadMultiRelationsFromDb(array $models, string $relation, bool $useRelations = false, array $withRelations = []): void
+    {
+        if (count($models) === 0) {
+            return;
+        }
+
+        $parentModelType = get_class($models[0]);
+        $relationModelsSetter = 'set' . str_replace('_', '', ucwords($relation, '_'));
+        [$relationModelType, $reverseRelation] = call_user_func([$parentModelType, 'getMultiRelations'])[$relation];
+        $reverseRelationIdGetter = 'get' . str_replace('_', '', ucwords($reverseRelation, '_')) . 'Id';
+
+        $parentModelsById = [];
+        foreach ($models as $model) {
+            $parentModelsById[$model->getId()] = $model;
+        }
+
+        $select = new Select($this->dbConnection);
+        $select->where($reverseRelation . '_id', 'IN', array_keys($parentModelsById));
+
+        $relationsByParentModelId = [];
+        foreach ($this->selectMultipleFromDb($select, $relationModelType, $useRelations, $withRelations) as $relationModel) {
+            $reverseRelationId = $relationModel->$reverseRelationIdGetter();
+            if (!isset($relationsByParentModelId[$reverseRelationId])) {
+                $relationsByParentModelId[$reverseRelationId] = [];
+            }
+            $relationsByParentModelId[$reverseRelationId][] = $relationModel;
+        }
+
+        foreach ($parentModelsById as $parentModelId => $parentModel) {
+            $relationModels = $relationsByParentModelId[$parentModelId] ?? [];
+            $parentModel->$relationModelsSetter($relationModels);
+        }
+    }
+
     public function saveToDb(Model $model): void
     {
         $this->syncRelations($model);