Laravel Eloquent:如何使用Pivot获取第三个表关系

class User extends Model
{
    public function roles()
    {
        return $this->belongsToMany(Role::class, 'user_role');
    }
}

class Role extends Model
{
    public function users()
    {
        return $this->belongsToMany(User::class, 'user_role');
    }
}

$user = User::find(1);
$roles = $user->roles;

class User extends Model
{
    public function roles()
    {
        return $this->belongsToMany(Role::class, 'user_role')
                    ->withPivot('created_at', 'updated_at');
    }
}

$user = User::find(1);
$roles = $user->roles;

foreach ($roles as $role) {
    echo $role->pivot->created_at;
    echo $role->pivot->updated_at;
}