DB::Table 与 Model::get() 上的 Laravel 或 PHP foreach 问题答案

【问题标题】：Laravel or PHP foreach issue on DB::Table vs. Model::get()DB::Table 与 Model::get() 上的 Laravel 或 PHP foreach 问题
【发布时间】：2021-01-19 05:19:46
【问题描述】：

下面的代码可以正常工作：

$data = Structures::select("id", "parent_id", "category", "type", "subType", "variant", "description")
        ->orderBy('category')
        ->orderBy('type')
        ->orderBy('subType')
        ->orderBy('variant')
        ->get() ;

        return $this->fillCategories($data) ;

fillCategories() 函数使用父子关系填充 JSON 树。

但是，下面的代码不起作用。

  $data = DB::table("categories AS t1")
        ->select("t1.id", "t1.name AS category", "t2.id as typeId", "t2.name as type", "t3.id as subTypeId", "t3.name as subType", "t4.id as variantId", "t4.name as variant")
          ->leftJoin("categories AS t2", "t2.parent_id", "=", "t1.id")
          ->leftJoin("categories AS t3", "t3.parent_id", "=", "t2.id")
          ->leftJoin("categories AS t4", "t4.parent_id", "=", "t3.id")
            ->whereNull("t1.parent_id")
              ->orderBy("t1.name")
              ->orderBy("t2.name")
              ->orderBy("t3.name")
              ->orderBy("t4.name")
            ->get() ;

            foreach ($data as $v) {
              Log::info("cat: " . json_encode($v));
            }

        return $this->fillCategories($data) ;

本地日志返回值，但是当$data传递给fillCategories()时，函数中的foreach忽略了$data！

fillCategories() 中 foreach 的片段

...
      $select = array() ;
      $child = array() ;

      $cat = null ;
      $type = null ;
      $sub = null ;
      $first = true ;

      $clear = true ;
      $label = null ;
      $value = null ;

      $prev = null ;

     Log::info("fillCat: data = " . json_encode($data)) ;

     foreach ($data as $v):

        Log::info("fillCat forloop: v($v->cat, $v->type, $v->subType, $v->variant)") ;

        $parent = null ;
        $isKid = false ;
        $isGrandKid = false ;

...

我现在假设将 $data 从 DB::table 而不是 Facades\App\Model\Structures::get() 传递给函数会在翻译中丢失。

【问题讨论】：

它们是不同的查询，可能一个没有返回任何结果
感谢您的评论。这是我最初的想法。他们都返回结果。我查过了。
那么这里还不够......你将一个集合传递给这个方法，如果它不为空，那么foreach 将运行（迭代它），所以根据你的正在显示集合必须为空才能到达该日志语句
[2020-10-04 08:13:42] local.INFO: fillCat: data = [{"id":11,"parent_id":null,"category":"Structure", "type":"Lampole","subType":null,"variant":null,"description":"Lampole"},{"id":13,"parent_id":11,"category":"Structure", "type":"Lampole","subType":"QB","variant"[2020-10-04 08:13:42] local.INFO: fillCat: data = [{"id":297,"category" :"建筑物","typeId":297,"type":"Cabin","subTypeId":null,"subType":null,"variantId":null,"variant":null},{"id":311 ,"category":"建筑物","typeId":311,"type":"守卫
好的，它正在达到它......那么问题是什么？

标签： php laravel eloquent php-7 laravel-7

【解决方案1】：

感谢 Faiz，显然 orderBy 是问题所在！（！）如果我把它拿出来，fillCategories()foreach 会处理数据。

$data = DB::table("categories AS t1")
        ->select("t1.id", ...)
          ->leftJoin("categories AS t2", "t2.parent_id", "=", "t1.id")
          ->leftJoin("categories AS t3", "t3.parent_id", "=", "t2.id")
          ->leftJoin("categories AS t4", "t4.parent_id", "=", "t3.id")
            ->whereNull("t1.parent_id")
              ->orderBy("t1.name")
              ->orderBy("t2.name")
              ->orderBy("t3.name")
            ->get() ;

这行得通。也许 Taylor Otwell 可以告诉我原因！

【讨论】：