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Laravel 5 eloquent hasManyThrough / belongsToManyThrough关系

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在Laravel 5.2应用程序中，我有三个模型： User ， Role 和 Task . User 与多个 Roles 关联， Role 与多个 Tasks 关联 . 因此，每个用户通过他们的角色与多个任务相关联 .

我试图通过他们的角色访问与 User 相关联的所有 Tasks .

我模型的相关部分如下：

class User extends Authenticatable
{    
    public function roles()
    {
        return $this->belongsToMany('App\Role');
    }

    public function tasks()
    {
        return $this->hasManyThrough('App\Task', 'App\Role');
    }
}

class Role extends Model
{
    public function tasks()
    {
        return $this->belongsToMany('App\Task');
    }

    public function users()
    {
        return $this->belongsToMany('App\User');
    }
}

class Task extends Model
{    
    public function roles()
    {
        return $this->belongsToMany('App\Role');
    } 
}

以下返回SQL错误;

Column not found: 1054 Unknown column 'roles.user_id'

它似乎试图通过Role模型中的（不存在的）外键来访问关系，而不是通过数据透视表 .

$user = Auth::user;
$tasks = $user->tasks;

如何通过这些关系访问与用户相关的所有任务？

php laravel laravel-5 eloquent many-to-many

2 回答

  • 1

    我开发了一个你可能感兴趣的custom BelongsToManyThrough relationship . 您需要添加新的关系类（在我的要点中给出;它在此处粘贴太长），并且还覆盖您的基础 Model 类，如实现 belongsToManyThrough 中所述 .

    然后（假设您使用的是Laravel的默认表命名方案 - 如果没有，您也可以指定连接表），您可以将关系定义为：

    public function tasks()
{
    return $this->belongsToManyThrough(
        'App\Task',
        'App\Role');
}

    belongsToManyThrough 不仅会为您提供用户的任务列表，还会告诉您每个用户每个任务的角色 . 例如，如果你有：

    $user->tasks()->get()

    输出看起来像：

    [
    {
        "id": 2,
        "name": "Ban spammers",
        "roles_via": [
            {
                "id": 2,
                "slug": "site-admin",
                "name": "Site Administrator",
                "description": "This role is meant for \"site administrators\", who can basically do anything except create, edit, or delete other administrators."
            },
            {
                "id": 3,
                "slug": "group-admin",
                "name": "Group Administrator",
                "description": "This role is meant for \"group administrators\", who can basically do anything with users in their same group, except other administrators of that group."
            }
        ]
    },
    {
        "id": 13,
        "name": "Approve posts",
        "roles_via": [
            {
                "id": 3,
                "slug": "group-admin",
                "name": "Group Administrator",
                "description": "This role is meant for \"group administrators\", who can basically do anything with users in their same group, except other administrators of that group."
            }
        ]
    },
    {
        "id": 16,
        "name": "Reboot server",
        "roles_via": [
            {
                "id": 2,
                "slug": "site-admin",
                "name": "Site Administrator",
                "description": "This role is meant for \"site administrators\", who can basically do anything except create, edit, or delete other administrators."
            }
        ]
    }
]

    我的自定义关系只有少量查询才能有效地执行此操作，而不是涉及 foreach 的其他解决方案，这会产生n+1 query问题 .

    回复于
  • 0

    从您共享的源代码中可以看出， User 和_2745444之间以及 Role 和 Task 之间存在 Many to Many 关系 .

    hasManyThrough 方法需要两个 One to Many 关系 .

    获取所有 User 相关 Task 的可能方法是:(在 User 类中）

    public function getTasksAttribute()
{
    $tasks = [];
    foreach ($this->roles as $role) {
        $tasks = array_merge($tasks, $role->tasks);
    }
    return $tasks;
 }

    然后，您可以使用以下命令访问任务：

    $user->tasks;
    回复于

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