Laravel委托具有角色的用户返回空数组

Question

我正在使用带有Zizaco Entrust库的Laravel 5.5。 https://github.com/Zizaco/entrust

我根据文档设置了角色，权限和用户模型。

用户表：

+----+-------+-----------------+--+
| id | name  |      email      |  |
+----+-------+-----------------+--+
|  2 | admin | admin@admin.com |  |
+----+-------+-----------------+--+

角色表

+----+-------+
| id | name  |
+----+-------+
|  1 | admin |
+----+-------+

role_user表

+---------+---------+
| user_id | role_id |
+---------+---------+
|       2 |       1 |
+---------+---------+

但是

$user = User::with('roles')->where('id', 4)->get();

为 roles

返回一个空数组

[
    {
        "id": 2,
        "name": "Admin",
        "email": "admin@admin.com",
        "created_at": "2018-11-07 11:11:24",
        "updated_at": "2018-11-07 11:24:51",
        "deleted_at": null,
        "company_id": 1,
        "active": true,
        "roles": []
    }
]

User.php

class User extends Authenticatable
{
    use EntrustUserTrait;
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password', 'company_id', 'active'
    ];

    protected $casts = [
        'active' => 'boolean',
    ];

    protected $hidden = [
        'password', 'remember_token'
    ];
}