Laravel正在尝试选择关系列的以下内容

Question

我有一个雄辩的模型App\list，它属于App\Product

public function product()
{
    return $this->belongsTo(Product::class);
}

在Listing Controller中，我试图从产品表中获取一个包含两列（name，keywords）的特定列表。

public function readListing(Request $request, $listingId)
{
    $query = Listing::query();
    $item = $query->with(['product' => function (Builder $query) {
        return $query->select(['name', 'keywords']);
    }])->findOrFail($listingId);
    return response()->json($item->toArray(), 200);
}

我得到这个错误：

传递给App\Http\Controller\API\ListingController::App\Http\Controller\API{闭包}（）的TypeError Argument 1必须是Illumate\Database\Eloquent\Builder的实例，Illumate\Database\Eloquent\关系\BelongsTo给定的实例，在...中调用...uilder.php580号线

580号线在哪里

$item = $query->with(['product' => function (Builder $query) {

当我像这样从行中删除类型声明时

$item = $query->with(['product' => function ($query) {

我得到一个结果，但它不包括product表中的两列（name，keywords）。

{
    id: 1,
    product_id: 1,
    listing_price: 10,
    actual_price: 5,
    in_stock: 1,
    listing_date: null,
    delisting_date: null,
    created_at: "2021-02-24T12:33:48.000000Z",
    updated_at: "2021-02-24T13:45:25.000000Z",
    deleted_at: null,
    category: "Fruits",
    category_id: 2,
    description: "Rem laudantium aut",
    image_urls: [
        ".../storage/products/February2021/CF3nzhmc0RXevSWdOJcd.jpg",
        ".../storage/products/February2021/oBtXf5kBjkAyrazuFDyu.jpg",
        ".../storage/products/February2021/GfpaGxSoGLA2FBqGrcDX.jpg"
    ],
    image_medium_urls: [
        ".../storage/products/February2021/CF3nzhmc0RXevSWdOJcd-medium.jpg",
        ".../storage/products/February2021/oBtXf5kBjkAyrazuFDyu-medium.jpg",
        ".../storage/products/February2021/GfpaGxSoGLA2FBqGrcDX-medium.jpg"
    ],
    image_small_urls: [
        ".../storage/products/February2021/CF3nzhmc0RXevSWdOJcd-small.jpg",
        ".../storage/products/February2021/oBtXf5kBjkAyrazuFDyu-small.jpg",
        ".../storage/products/February2021/GfpaGxSoGLA2FBqGrcDX-small.jpg"
    ],
    thumbnail_url: ".../storage/products/February2021/CF3nzhmc0RXevSWdOJcd-small.jpg",
    product: null
}

为什么类型声明会导致问题，如何让它从相关表中选择这两列？




Answer 1

您需要在案例中包含foreign_keylisting_id

    $query = Listing::with(['product' => function ($query) {
    // add listing_id
        return $query->select(['listing_id', 'name', 'keywords']);
    }])
        ->findOrFail($listingId);

这一点在laravel文档中有所提及

使用此功能时，应始终在要检索的列列表中包含id列和任何相关外键列。