Laravel 4:如果关系存在通过查询关系选择行 [英] Laravel 4: Select row if a relation exists by querying relation

问题描述

我正在尝试查询产品表，并希望它在关系存在时返回一个集合.

I am trying to query a products table, and want it to return a collection if a relation exists.

迭代1查询products表中的所有行，如果$name匹配，则延迟加载metals表.这是错误的.

Iteration 1 below queries all rows in the products table, and lazy loads the metals table if $name matches. This is wrong.

我的路线:

Route::group(array('prefix' => '{api}/v1'), function()
{
    Route::controller('products', 'ApiV1ProductController');
});

我的控制器:

public function getFilter($metal = null) {
    $products = $this->product;
    if ($metal) {
        $products->with('metal', function($query, $metal) {
            $query->where('name', $metal);
        });
    }
    return Response::api($products->get());
} 

如果metal.name = $metal，我希望仅 $products 显示.例如类似:

I want only $products to display if metal.name = $metal. e.g. something like:

$this->products->where('metal.name', $metal)->get;

使用 Glad To Help 部分答案的解决方案:

这提供了一种替代方法 2，无需连接.

This provides an alternative approach 2, without the need for joins.

http://paste.laravel.com/WC4

推荐答案

不幸的是，您还不能在 Eloquent 中通过一次滑动来完成此操作.

Unfortunately you cannot do this with one swipe in Eloquent yet.

但是，有一种使用逆关系的方法，如下所示:

BUT, there is a way by using the inverse relation, like this:

public function getFilter($metal = null)
{
    // filter the metals first
    $metals = Metal::with('products')->where('name', '=' , $metal)->get();
    $products = array();
    foreach($metals as $metal)
    {
           // collect the products from the filtered metals
           $products = array_merge($products, $metal->products->toArray() );
    }
    return $products;
}

如果这对您来说不是一个优雅的解决方案，您将不得不使用 Fluent 来构建查询并手动加入 products x metal 表，或者通过覆盖 newQuery() 方法预先加入它们.

If this is not elegant solution for you, you will either have to use Fluent to construct the query and join the products x metals table manually or pre-join them by overriding the newQuery() method.

1) 替代方法一.

public function getFilter($metal = null) {
    return DB::table('products')->join('metal', 'products.id', '=' , 'metal.product_id')
                         ->where('metal.name', $name)
                         ->select(array('products.*'));
}

2) 替代方法二

class Product extends Eloquent{

public function newQuery($excludeDeleted = true){
        return parent::newQuery()->join('metal','id','=','metal.product_id');
    }

}

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