Laravel 在关系对象上的位置

问题描述

我正在使用 Laravel 5.0 开发 Web API，但我不确定我正在尝试构建的特定查询.

I'm developing a web API with Laravel 5.0 but I'm not sure about a specific query I'm trying to build.

我的课程如下:

class Event extends Model {

    protected $table = 'events';
    public $timestamps = false;

    public function participants()
    {
        return $this->hasMany('AppParticipant', 'IDEvent', 'ID');
    }

    public function owner()
    {
        return $this->hasOne('AppUser', 'ID', 'IDOwner');
    }
}

和

class Participant extends Model {

    protected $table = 'participants';
    public $timestamps = false;

    public function user()
    {
        return $this->belongTo('AppUser', 'IDUser', 'ID');
    }

    public function event()
    {
        return $this->belongTo('AppEvent', 'IDEvent', 'ID');
    }
}

现在，我想获取特定参与者的所有事件.我试过:

Now, I want to get all the events with a specific participant. I tried with:

Event::with('participants')->where('IDUser', 1)->get();

但是 where 条件应用于 Event 而不是它的 Participants.以下给了我一个例外:

but the where condition is applied on the Event and not on its Participants. The following gives me an exception:

Participant::where('IDUser', 1)->event()->get();

我知道我可以写这个:

$list = Participant::where('IDUser', 1)->get();
for($item in $list) {
   $event = $item->event;
   // ... other code ...
}

但是向服务器发送这么多查询似乎效率不高.

but it doesn't seem very efficient to send so many queries to the server.

使用 Laravel 5 和 Eloquent 通过模型关系执行 where 的最佳方法是什么?

What is the best way to perform a where through a model relationship using Laravel 5 and Eloquent?

推荐答案

对您的关系执行此操作的正确语法是:

The correct syntax to do this on your relations is:

Event::whereHas('participants', function ($query) {
    return $query->where('IDUser', '=', 1);
})->get();

这将返回参与者的用户 ID 为 1 的事件.如果参与者的用户 ID 不为 1，则不会返回该事件.

This will return Events where Participants have a user ID of 1. If the Participant doesn't have a user ID of 1, the Event will NOT be returned.

在 https://laravel.com/docs/5.8/eloquent 阅读更多-relationships#eager-loading

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