diff --git a/app/Http/Controllers/CategoriesController.php b/app/Http/Controllers/CategoriesController.php
index 7fab3b465..ee493478a 100644
--- a/app/Http/Controllers/CategoriesController.php
+++ b/app/Http/Controllers/CategoriesController.php
@@ -8,10 +8,13 @@
 
 class CategoriesController extends Controller
 {
-    public function show(Category $category)
+    public function show(Category $category, Request $request, Topic $topic)
     {
         // 读取分类 ID 关联的话题，并按每 20 条分页
-        $topics = Topic::where('category_id', $category->id)->paginate(20);
+        $topics = $topic->withOrder($request->order)
+                        ->where('category_id', $category->id)
+                        ->paginate(20);
+
         // 传参变量话题和分类到模板中
         return view('topics.index', compact('topics', 'category'));
     }
diff --git a/app/Http/Controllers/TopicsController.php b/app/Http/Controllers/TopicsController.php
index 1263aeeec..88be36218 100644
--- a/app/Http/Controllers/TopicsController.php
+++ b/app/Http/Controllers/TopicsController.php
@@ -14,11 +14,11 @@ public function __construct()
         $this->middleware('auth', ['except' => ['index', 'show']]);
     }
 
-	public function index()
-	{
-        $topics = Topic::with('user', 'category')->paginate(30);
+    public function index(Request $request, Topic $topic)
+    {
+        $topics = $topic->withOrder($request->order)->paginate(20);
         return view('topics.index', compact('topics'));
-	}
+    }
 
     public function show(Topic $topic)
     {
diff --git a/app/Models/Topic.php b/app/Models/Topic.php
index 179fd97e8..f43c7a00b 100644
--- a/app/Models/Topic.php
+++ b/app/Models/Topic.php
@@ -18,4 +18,33 @@ public function user()
     {
         return $this->belongsTo(User::class);
     }
+
+    public function scopeWithOrder($query, $order)
+    {
+        // 不同的排序，使用不同的数据读取逻辑
+        switch ($order) {
+            case 'recent':
+                $query->recent();
+                break;
+
+            default:
+                $query->recentReplied();
+                break;
+        }
+        // 预加载防止 N+1 问题
+        return $query->with('user', 'category');
+    }
+
+    public function scopeRecentReplied($query)
+    {
+        // 当话题有新回复时，我们将编写逻辑来更新话题模型的 reply_count 属性，
+        // 此时会自动触发框架对数据模型 updated_at 时间戳的更新
+        return $query->orderBy('updated_at', 'desc');
+    }
+
+    public function scopeRecent($query)
+    {
+        // 按照创建时间排序
+        return $query->orderBy('created_at', 'desc');
+    }
 }
diff --git a/resources/views/topics/index.blade.php b/resources/views/topics/index.blade.php
index 3f9e732d0..b31f74629 100644
--- a/resources/views/topics/index.blade.php
+++ b/resources/views/topics/index.blade.php
@@ -16,8 +16,16 @@
 
       <div class="card-header bg-transparent">
         <ul class="nav nav-pills">
-          <li class="nav-item"><a class="nav-link active" href="#">最后回复</a></li>
-          <li class="nav-item"><a class="nav-link" href="#">最新发布</a></li>
+          <li class="nav-item">
+            <a class="nav-link {{ active_class( ! if_query('order', 'recent')) }}" href="{{ Request::url() }}?order=default">
+              最后回复
+            </a>
+          </li>
+          <li class="nav-item">
+            <a class="nav-link {{ active_class(if_query('order', 'recent')) }}" href="{{ Request::url() }}?order=recent">
+              最新发布
+            </a>
+          </li>
         </ul>
       </div>