在hasMany关系上获取特定字段

本文介绍了在hasMany关系上获取特定字段的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个像这样的 hasMany 关系函数:

I have a hasMany relation function like this:

public function articles() { return $this->hasMany('App\Article'); }

并像这样使用它:

$data = \App\User::with('articles')->get();

我没有任何问题，因为它正在返回预期的数据.像这样:

I don't have any problems with it, since it's returning the expected data. Something like this:

{ "id": 1, "name": "Jhon", "lastname": "Doe", "articles": [ { "id": 1, "title": "Article 1", "status": "published", "published_at": "2015-04-30" }, { "id": 2, "title": "Article 2", "status": "draft", "published_at": null } ] }

我想要实现的目标，但我仍然不能仅获取关系字段的子集来获取此信息:

What I am trying to achieve but I still can't it's to fetch just a subset of the relation's fields to obtain this:

{ "id": 1, "name": "Jhon", "lastname": "Doe", "articles": [ { "id": 1, "title": "Article 1" }, { "id": 2, "title": "Article 2" } ] }

我的目的是找到一种在模型函数中指定字段子集的方法，而不是迭代返回的集合并取消设置不需要的字段.

My intention is to find a way to specify the subset of fields in the Model's function instead of iterating the returning collection and unset the unwanted fields.

这可能吗?

推荐答案

您有几个选择:

使用时修改关系查询. with()方法可以接受键/值对的数组，其中键是关系的名称，值是用于修改关系查询的闭包.

Modify the relationship query when using it. The with() method can accept an array of key/value pairs where the key is the name of the relationship and the value is a Closure that modifies the relationship query. $data = \App\User::with(['articles' => function($query) { $query->select(['id', 'title', 'user_id']); }])->get();

创建一个包含所需字段的新关系.

Create a new relationship that contains the fields you want.

public function articleTitles() { return $this->hasMany('App\Article')->select(['id', 'title', 'user_id']); } $data = \App\User::with('articleTitles')->get();

如果仅关注array/json输出，则可以修改App \ Article模型以仅在转换为数组时显示id和标题.

If you're only concerned about the array/json output, you can modify the App\Article model to only display the id and title when converted to an array.

class Article extends Model { protected $visible = ['id', 'title']; }

选择什么取决于您的需求.

What you choose depends on what you need.

注意:对于上述选项1和2，必须选择外键(user_id)，以便Laravel知道在建立关系时如何将模型链接在一起.

NB: For options 1 and 2 above, the foreign key (user_id) must be selected so that Laravel knows how to link the models together when building the relationships.