Php 删除未分类的帖子后，如何将其分配给原始类别

我正在从事一个laravel博客项目，如果我删除了一个类别，我希望这个类别的所有文章都转移到“未分类”类别。如果文章属于已删除的类别和其他类别，则避免将该文章移至未分类，否则将该文章移至未分类。 我使用多对多的分类后模型的关系。请参见下面的我的代码：

迁移后我有

Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->foreignId('user_id')
    ->constrained()
    ->onDelete('cascade');

    $table->string('title')->unique();
    $table->string('featured_image')->nullable()->default('default_featured_image.jpg');
    $table->text('detail');
    $table->string('tags')->nullable();
    $table->timestamps();
});

类别迁移

public function up()
{
    Schema::create('categories', function (Blueprint $table) {
        $table->id();
        $table->string('title');
        $table->text('detail',300)->nullable();
        $table->string('image')->nullable();
        $table->timestamps();
    });
}

关系的轴心迁移

public function up()
{
    Schema::create('category_post', function (Blueprint $table) {
        $table->id();
        $table->unsignedInteger('post_id');
        $table->unsignedInteger('category_id');
        $table->timestamps();
    });
}

public function up()
{
    Schema::create('category_post', function (Blueprint $table) {
        $table->id();
        $table->unsignedInteger('post_id');
        $table->unsignedInteger('category_id');
        $table->timestamps();
        $table->foreignId('category_id')
            ->constrained(categories)
            ->onUpdate('cascade')
            ->onDelete('cascade');
        $table->foreignId('post_id')
            ->constrained(posts)
            ->onUpdate('cascade')
            ->onDelete('cascade');

    });
}

后期模型

 function categories(){
    return $this->belongsToMany(Category::class);
 }   

function posts(){
   return $this->belongsToMany(Post::class);
}

类别模型

 function categories(){
    return $this->belongsToMany(Category::class);
 }   

function posts(){
   return $this->belongsToMany(Post::class);
}

类别控制器

public function destroy(Request $request)
{
   $cat_id = $request->category_id;
   $category = Category::find($cat_id);

   $posts_to_update_category_id = $category->posts()->wherePivot('category_id','=',$cat_id)->get();
   foreach($posts_to_update_category_id as $post){
       $post = Post::find($post->id);
       $post->categories()->sync(1); //uncategorized id = 1
   }
   

   $category->delete();
   return redirect('admin/category')->with('success', ''.$category->title.' has been Deleted');
}   

我对代码的问题是，它最终会将所有已删除类别id的帖子更新为1（未分类）。也就是说，如果我有一篇文章有两个不同的类别，比如cat1和cat2，我删除cat1，我不希望这篇文章被移动到未分类的位置，但是我的代码确实移动了它，并且从中删除了cat2，使它只是未分类。如果可以的话，请帮忙。谢谢

$category->posts（）->wherePivot（'category_id'，'='，$cat_id）->get（）

已经返回posts实例，因此您不必执行

$post=post:：find（$post->id）稍后

您可以验证它是否有多个类别，这意味着此帖子不应移动到未分类，而应删除该类别，对吗

所以你可以这样做

public function destroy(Request $request)
{
   $cat_id = $request->category_id;
   $category = Category::find($cat_id);

   $posts = $category->posts()->with('categories')->wherePivot('category_id','=',$cat_id)->get();
   foreach($posts as $post){
       if (count($post->categories) > 1) {
           $post->categories()->detach($cat_id);
       } else {
           $post->categories()->sync(1); //uncategorized id = 1
       }
   }
   

   $category->delete();
   return redirect('admin/category')->with('success', ''.$category->title.' has been Deleted');
}  

一个简单的解决方案是在删除类别时删除关系

关系的轴心迁移

public function up()
{
    Schema::create('category_post', function (Blueprint $table) {
        $table->id();
        $table->unsignedInteger('post_id');
        $table->unsignedInteger('category_id');
        $table->timestamps();
    });
}

public function up()
{
    Schema::create('category_post', function (Blueprint $table) {
        $table->id();
        $table->unsignedInteger('post_id');
        $table->unsignedInteger('category_id');
        $table->timestamps();
        $table->foreignId('category_id')
            ->constrained(categories)
            ->onUpdate('cascade')
            ->onDelete('cascade');
        $table->foreignId('post_id')
            ->constrained(posts)
            ->onUpdate('cascade')
            ->onDelete('cascade');

    });
}

当您删除帖子或类别时，关系将被数据库中的cascade Automatically删除
为什么要创建一个名为
未分类的类别
，只需将其设置为当它没有类别时，它是未分类的。非常感谢您的帮助me@Richie很高兴它成功了，如果可以的话，把我的答案标记为正确，这样其他有同样问题的人就可以看到什么对你有用了。非常感谢much@Richie如果答案对您有帮助，请将其设置为“正确答案”，这样您的问题将被标记为“已结束”