Add toTree() method

README.md

@@ -33,6 +33,7 @@ Supports Laravel 5.5.29+.
 - [Depth](#depth)
 - [Path](#path)
 - [Custom Paths](#custom-paths)
+- [Nested Results](#nested-results)
 
 ### Getting Started
 
@@ -328,6 +329,50 @@ echo $descendantsAndSelf[1]->slug_path; // user-1/user-2
 echo $descendantsAndSelf[2]->slug_path; // user-1/user-2/user-3
 ```
 
+# Nested Results
+
+Use the `toTree()` method on the result collection to generate a nested tree:
+
+```php
+$users = User::tree()->get();
+
+$tree = $users->toTree();
+```
+
+This recursively sets `children` and `parent` relationships:
+
+```json
+[
+  {
+    "id": 1,
+    "children": [
+      {
+        "id": 2,
+        "children": [
+          {
+            "id": 4,
+            "children": [],
+            "parent": {
+              "id": 2
+            }
+          }
+        ],
+        "parent": {
+          "id": 1
+        }
+      },
+      {
+        "id": 3,
+        "children": [],
+        "parent": {
+          "id": 1
+        }
+      }
+    ]
+  }
+]
+```
+
 ## Contributing
 
 Please see [CONTRIBUTING](.github/CONTRIBUTING.md) and [CODE OF CONDUCT](.github/CODE_OF_CONDUCT.md) for details.

src/Eloquent/Collection.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace Staudenmeir\LaravelAdjacencyList\Eloquent;
+
+use Illuminate\Database\Eloquent\Collection as Base;
+
+class Collection extends Base
+{
+    public function toTree($childrenRelation = 'children', $parentRelation = 'parent')
+    {
+        if ($this->isEmpty()) {
+            return $this;
+        }
+
+        $parentKeyName = $this->first()->getParentKeyName();
+        $localKeyName = $this->first()->getLocalKeyName();
+        $depthName = $this->first()->getDepthName();
+
+        $depths = $this->pluck($depthName);
+
+        $tree = new static(
+            $this->where($depthName, $depths->min())->values()
+        );
+
+        $itemsByParentKey = $this->groupBy($parentKeyName);
+        $itemsByLocalKey = $this->keyBy($localKeyName);
+
+        foreach ($this->items as $item) {
+            $item->setRelation($childrenRelation, $itemsByParentKey[$item->$localKeyName] ?? new static());
+
+            if (isset($item->$parentKeyName, $itemsByLocalKey[$item->$parentKeyName])) {
+                $item->setRelation($parentRelation, $itemsByLocalKey[$item->$parentKeyName]);
+            }
+        }
+
+        return $tree;
+    }
+}

src/Eloquent/HasRecursiveRelationships.php

@@ -416,4 +416,15 @@ public function newEloquentBuilder($query)
     {
         return new \Staudenmeir\LaravelAdjacencyList\Eloquent\Builder($query);
     }
+
+    /**
+     * Create a new Eloquent Collection instance.
+     *
+     * @param array $models
+     * @return \Staudenmeir\LaravelAdjacencyList\Eloquent\Collection
+     */
+    public function newCollection(array $models = [])
+    {
+        return new Collection($models);
+    }
 }

tests/CollectionTest.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Tests;
+
+use Tests\Models\User;
+
+class CollectionTest extends TestCase
+{
+    public function testToTree()
+    {
+        $users = User::tree()->orderBy('id')->get();
+
+        $tree = $users->toTree();
+
+        $this->assertEquals([1, 11], $tree->pluck('id')->all());
+        $this->assertFalse($tree[0]->relationLoaded('parent'));
+        $this->assertEquals([2, 3, 4], $tree[0]->children->pluck('id')->all());
+        $this->assertTrue($tree[0]->children[0]->relationLoaded('parent'));
+        $this->assertEquals(1, $tree[0]->children[0]->parent->id);
+        $this->assertEquals([5], $tree[0]->children[0]->children->pluck('id')->all());
+        $this->assertEquals([8], $tree[0]->children[0]->children[0]->children->pluck('id')->all());
+        $this->assertEquals([12], $tree[1]->children->pluck('id')->all());
+    }
+
+    public function testToTreeWithDescendants()
+    {
+        $users = User::find(1)->descendants()->orderBy('id')->get();
+
+        $tree = $users->toTree();
+
+        $this->assertEquals([2, 3, 4], $tree->pluck('id')->all());
+        $this->assertFalse($tree[0]->relationLoaded('parent'));
+        $this->assertEquals([5], $tree[0]->children->pluck('id')->all());
+        $this->assertTrue($tree[0]->children[0]->relationLoaded('parent'));
+        $this->assertEquals(2, $tree[0]->children[0]->parent->id);
+        $this->assertEquals([8], $tree[0]->children[0]->children->pluck('id')->all());
+    }
+
+    public function testToTreeWithEmptyCollection()
+    {
+        $users = User::tree(1)->where('id', 0)->get();
+
+        $tree = $users->toTree();
+
+        $this->assertEmpty($tree);
+    }
+}