Php Laravel get（）与（）

拉威尔5.5。当我像这样使用控制器时：

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('ad')->get();

{"id":1,"ad_id":"1","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":1,"title":"Test 1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":2,"ad_id":"2","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":2,"title":"Test 2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":3,"ad_id":"3","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":3,"title":"Test 3","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":4,"ad_id":"4","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":4,"title":"Test 4","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('category')->get();

我看到的是这样的景象：

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('ad')->get();

{"id":1,"ad_id":"1","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":1,"title":"Test 1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":2,"ad_id":"2","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":2,"title":"Test 2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":3,"ad_id":"3","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":3,"title":"Test 3","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":4,"ad_id":"4","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":4,"title":"Test 4","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('category')->get();

CategoryItem模型同时属于Ad类和Category类

但是，当我尝试使用Category获取CategoryItem时，我的意思是：

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('ad')->get();

{"id":1,"ad_id":"1","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":1,"title":"Test 1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":2,"ad_id":"2","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":2,"title":"Test 2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":3,"ad_id":"3","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":3,"title":"Test 3","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

{"id":4,"ad_id":"4","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","ad":{"id":4,"title":"Test 4","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00"}}

$ad = Ad::get();
$category = Category::get();
$categoryItem = CategoryItem::get();

$c = CategoryItem::with('category')->get();

我得到了这个视图，类别对象旁边有NULL：

{"id":1,"ad_id":"1","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","category":null}

{"id":2,"ad_id":"2","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","category":null}

{"id":3,"ad_id":"3","cat_id":"1","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","category":null}

{"id":4,"ad_id":"4","cat_id":"2","created_at":"2017-10-14 00:00:00","updated_at":"2017-10-14 00:00:00","category":null}

分类模型有许多广告和分类项

---

我真正想做的是能够通过CategoryItem获得广告和分类，包括标题、ID和其他信息。。。我只需要理解这一点，以便以后可以将通过ID获取项目更改为通过段塞名称获取项目

由于您使用的是自定义外键名称

cat\u id

而不是

category\u id

，要使代码正常工作，您需要在关系定义中指定外键：

public function category()
{
    return $this->belongsTo(Category::class, 'cat_id');
}

Eloquent通过检查关系方法的名称并在方法名称后面加上

\u id

来确定默认外键名称。您可以将自定义键名作为第二个参数传递给

belongsTo

方法