如何獲取 Laravel 中父類別的所有子類別？

Question

我在$categories變量中有所有父類別，在$subCats變量中有所有子類別。 問題是，除了子類別之外，空的父類別也落入$subCats變量中。 你怎么能解決這個問題？

public function showForm() 
{
    $subCats = [];

    $categories = Category::where('parent_slug', null)->get();
    foreach($categories as $cats) {
        $subCats[] = Category::where('parent_slug', $cats->slug)->get();
    }

    return view('user.form', compact('categories', 'subCats'));
}

Answer 1

嘗試這個：

    public function showForm() 
    {
        $subCats = [];
    
        $categories = Category::where('parent_slug', null)->get();
        foreach($categories as $cats) {
           $subCat = Category::where('parent_slug', $cats->slug)->get();
           if($subCat->count()) {
             $subCats[] = $subCat;
           }
        }
    
        return view('user.form', compact('categories', 'subCats'));
    }

Answer 2

我認為您不需要循環：

$categories = Category::where('parent_slug', null)->get();
$subCats = Category::where('parent_slug', '!=', null)->get();

return view('user.form', compact('categories', 'subCats'));

為了獲得更高的性能，您可以在集合上使用whereNull()方法進行過濾：

$data = Category::get();

$categories = $data->whereNull('parent_slug')->all();
$subCats = $data->whereNotNull('parent_slug')->all();

return view('user.form', compact('categories', 'subCats'));