laravel在创建父模型后急于使用with()vs load()进行加载 [英] laravel eager loading using with() vs load() after creating the parent model

问题描述

我正在创建一个回复模型，然后尝试返回具有所有者关系的对象.这是返回空对象的代码:

I am creating a Reply model and then trying to return the object with it's owner relation. Here is the code that returns an empty object:

//file: Thread.php
//this returns an empty object !!??
public function addReply($reply)
{
    $new_reply = $this->replies()->create($reply);
    return $new_reply->with('owner');
}

但是，如果我将 with()方法换为 load()方法以加载 owner 关系，我会得到预期的结果.那就是返回的回复对象及其关联的所有者关系:

However, if i swap the with() method for load() method to load the owner relation, i get the expected result. That is the reply object is returned with it's associated owner relation:

//this works
{
    $new_reply = $this->replies()->create($reply);
    return $new_reply->load('owner');
}

我不明白为什么.寻找澄清.

i don't understand why. Looking for clarifications.

谢谢， Yeasir

Thanks, Yeasir

推荐答案

这是因为当您还没有对象(正在查询)时，应该使用with；而当您已经有对象时，应该使用with使用load.

This is because you should use with when you don't have object yet (you are making query), and when you already have an object you should use load.

示例:

用户集合:

$users = User::with('profile')->get();

或:

$users = User::all();
$users->load('profile');

单个用户:

$user = User::with('profile')->where('email','[e-mail]')->first();

或

$user = User::where('email','[e-mail]')->first();
$user->load('profile');

Laravel中的方法实现

还可以查看with方法的实现:

Also you can look at with method implementation:

public static function with($relations)
{
    return (new static)->newQuery()->with(
        is_string($relations) ? func_get_args() : $relations
    );
}

因此它将开始新的查询，因此实际上直到您使用get，first等，它才会执行查询，而load的实现方式如下:

so it's starting new query so in fact it won't execute the query until you use get, first and so on where is load implementation is like this:

public function load($relations)
{
    $query = $this->newQuery()->with(
        is_string($relations) ? func_get_args() : $relations
    );

    $query->eagerLoadRelations([$this]);

    return $this;
}

因此它返回了相同的对象，但是它加载了该对象的关系.

so it's returning the same object, but it load relationship for this object.

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