Laravel Eloquent 从关系中选择
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Laravel Eloquent select from relationship
提问by RGweb
I've been trying to get the hang of Laravel. I'm using Laravel 4. Right now I have two tables, a 'Products' table and a 'Images' table. A product can have many images and an image belongs to a product.
我一直在努力掌握 Laravel 的窍门。我正在使用 Laravel 4。现在我有两个表，一个“产品”表和一个“图像”表。一个产品可以有多个图片，一个图片属于一个产品。
So I have two models:
所以我有两个模型：
class Product extends Eloquent {
public function images()
{
return $this->hasMany('Image');
}
}
class Image extends Eloquent {
protected $table = 'product_images';
public function product()
{
return $this->belongsTo('Product');
}
}
Now I'm building the 'index' page of a resource, so I do Product::all() in the controller and send this to the view.
现在我正在构建资源的“索引”页面，因此我在控制器中执行 Product::all() 并将其发送到视图。
In the view I do a foreach and loop over all products. But now I want to get an image to show with the product. But I can't seem to figure out how to get, for instance, the first image.
在视图中，我执行 foreach 并遍历所有产品。但现在我想要一张图片来展示产品。但我似乎无法弄清楚如何获得，例如，第一张图片。
When I do $product->imagesI get an object of all images related to the product.
当我这样做时，$product->images我会得到与产品相关的所有图像的对象。
When I do $product->images->urlI get an error (Undefined property 'url')
当我这样做时，$product->images->url我收到一个错误（未定义的属性“url”）
I've tried $product->images->first()->urlthis also gives an error (Trying to get property of non-object)
我试过$product->images->first()->url这也给出了一个错误（试图获取非对象的属性）
What am I doing wrong?
我究竟做错了什么？
采纳答案by Dwight
The imagesproperty is an array-like property that you can loop through.
该images属性是一个类似数组的属性，您可以循环遍历。
foreach ($product->images as $image) {
echo $image->url;
}
Alternatively, if you only wanted the first, you can access the index.
或者，如果您只想要第一个，则可以访问索引。
$product->images[0]->url;
回答by Max Ehsan
Have you tried eager-loading?
你试过急切加载吗？
foreach (Product::with('images')->get() as $product)
{
echo $product->images->first()->url;
}
回答by Marko Aleksi?
You can try using the following PHP function.
您可以尝试使用以下 PHP 函数。
$first_image = array_shift($product->images);
Then, $first_image will be one image object, and accessing the URL of the image should be easy: $first_image->ulr
然后， $first_image 将是一个图像对象，并且访问图像的 URL 应该很容易： $first_image->ulr
Note: Haven't tested it, but should work. Let us know.
注意：还没有测试过，但应该可以工作。让我们知道。
