Laravel 5.5 通过嵌套关系检索空值

Question

我有 3 个数据库：

路线： id name

率：

Id
Route_id
Car_id

汽车：

id
name

我的路由模型

public function rates()
{
    return $this->hasMany('AppRate', 'route_id');
}

我的费率模型

public function car() {
    return $this->belongsTo('AppCar','car_id');
}

现在我需要访问汽车关系，但是当我这样做时

return $this->route->with('from','to','rates.car')->paginate(74);

我得到汽车关系的空

{"id":1,"from_id":1,"to_id":2,"distance":400,"created_at":null,"updated_at":null,"from":{"id":1,"name":"u0410u043au043au043e","created_at":null,"updated_at":null,"lat":32.93310000000000314912540488876402378082275390625,"long":35.0827000000000026602720026858150959014892578125},"to":{"id":2,"name":"u0410u0440u0430u0434","created_at":null,"updated_at":null,"lat":31.261399999999998300381776061840355396270751953125,"long":35.21490000000000009094947017729282379150390625},"rates":[{"id":1,"route_id":1,"car_id":1,"rate":1123,"night_rate":1391,"car":null},{"id":5551,"route_id":1,"car_id":2,"rate":1123,"night_rate":1391,"car":null},{"id":11101,"route_id":1,"car_id":3,"rate":1123,"night_rate":1391,"car":null},{"id":16651,"route_id":1,"car_id":4,"rate":1123,"night_rate":1391,"car":null},{"id":22201,"route_id":1,"car_id":5,"rate":1123,"night_rate":1391,"car":null},{"id":27751,"route_id":1,"car_id":6,"rate":1123,"night_rate":1391,"car":null},{"id":33301,"route_id":1,"car_id":7,"rate":1123,"night_rate":1391,"car":null},{"id":38851,"route_id":1,"car_id":8,"rate":1123,"night_rate":1391,"car":null}]},

Answer 1

据我了解，您正在尝试通过路线模型访问汽车模型。

我注意到的几件事应该可以帮助您找到解决方案。

首先，我认为您应该使用belongToMany()函数来反比。

public function car() {
    return $this->belongsToMany('AppCar','Rates'); // Perhaps call the table something like routes_cars to more clearly define it's a pivot table
}

接下来，我看到您正在尝试在$this()的上下文中使用模型函数。我假设您正在模型中执行此操作？该逻辑应该在控制器中，这可能会导致一些不希望的结果，但我不完全确定。此外，使用with()时，您的参数似乎不正确。 您可以使用在 belongsToMany() 中定义的函数名称

App/Route::with('car')->paginate(74);

使用正确的关系设置，您几乎不需要担心数据透视表。如果您要在数据透视表中添加额外的信息，则文档中有一些 laravel 函数可以帮助您执行此操作。