急切负载有许多 &属于(循环引用/无限循环) [英] Eager load hasMany & belongsTo (circular reference/infinite loop)

问题描述

更新(解决方案)

• 如果您需要 $user->images 内的 $image 之一的 ->user 关系，则 $user 变量已经可用，因为您从中加载了 ->images！
• 不要使用 protected $with Eloquent 属性.这是一种反模式.
• 相反，在需要的地方/时间按需显式地按需加载关系(注意:它不应该阻止您保持干燥！)
• 如果您确实需要/想要，请参阅@nicksonyap 的答案.它确实有效(我相信 - 未经测试).

• If you need ->user relationship from one of the $image inside $user->images, then $user variable is already available cause you loaded the ->images from it!
• Don't use protected $with Eloquent property. It's an anti-pattern.
• Instead explicitly eager load relationships on-demand from where/when it's needed (Note: it should not prevent you to keep things DRY!)
• If you really need/want to, see @nicksonyap answer. It does the trick (I believe – not tested).

原创

我遇到了一个我认为很简单的问题:

I'm running into what I believe is a simple problem:

• 我有一个 User 对象，它有很多 Images
• Image 属于 User...(逆关系)

• I have a User object that has many Images
• Image belongs to User... (inverse relation)

我的问题是我想同时加载 User 模型上的 images() 和 user()代码>图像模型.为此，我只需按照文档中的说明设置一个 $with 属性.

My problem is that I want to eager load both the images() on the User model and the user() on the Image model. To do so, I just setup a $with property as explained in the docs.

我的用户模型:

class User extends EloquentModel {
    protected $with = ['images'];

    public function images()
    {
        return $this->hasMany(Image::class);
    }
}

我的图片模型:

class Image extends EloquentModel {
    protected $with = ['user'];

    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

但是在表演时:

$user = User::find(203);

这会导致无限循环(php 分段错误).一定有某种我无法找到的循环引用:

This results in an infinite loop (php segmentation fault). There must be some kind of circular reference that I am not able to locate:

[1]    85728 segmentation fault

编辑 2016/02

这是我发现的最简单的解决方法":

This is the simplest "Workaround" I found:

// User.php
public function setRelation($relation, $value)
{
    if ($relation === 'images') {
        foreach ($value as $image) {
            $image->setUser($this);
        }
    }
    return parent::setRelation($relation, $value);
}

推荐答案

有一个 without() 方法:https://laravel.com/api/5.8/Illuminate/Database/Eloquent/Builder.html#method_without

将 without() 放在关系的双方都有效.

Placing without() on both sides of a relationship worked.

class Property extends EloquentModel {
    protected $with = ['images'];

    public function images()
    {
        return $this->hasMany(Image::class)->without('property');
    }
}

class Image extends EloquentModel {
    protected $with = ['property'];

    public function property()
    {
        return $this->belongsTo(Property::class)->without('images');
    }

    public function getAlt()
    {
        return $this->property->title;
    }
}

更新:

尽管使用 without() 很容易避免无限循环问题，但通过多年使用 Laravel 的经验，我意识到在模型中设置 $with 是不好的做法它导致关系总是加载.因此导致循环引用/无限循环

Even though using without() easily avoid the infinite loop issue, through years of experience with Laravel I realize it is bad practice to set $with in the model as it causes relationships to always load. Hence leading to circular reference/infinite loop

相反，总是使用 with() 来明确指定 需要立即加载的必要关系，无论多么必要(关系的关系)

Rather, always use with() to explicitly specify necessary relationships to be eager loaded, however deep necessary (relationship of relationship)

例如:

$user = User::with('images' => function ($query) {
            $query->with('property' => function ($query) {
                $query->with('deeperifneeded' => function ($query) {
                    //...
                });
            });
        ]);

注意:可能需要去掉without()

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