Laravel Eloquent 关系的限制结果

Laravel Eloquent limit results for relationship(Laravel Eloquent 关系的限制结果)

问题描述

我有一个简单的相册和图片设置，每个相册都有很多图片.我可以正常获取所有数据，但我想将返回的图像数量限制为 3.我尝试过像这样传递闭包:

I have a simple set-up of Albums and Images, each album has many images. I can get all the data fine but I want to limit the returned number of images to 3. I have tried passing a closure like so:

Album::with(['images' =>  function($query) { $query->take(3);}])->get();

这确实将图像数量限制为 3，但将图像总数限制为 3，但我想将每个相册限制为 3 个图像.所以第一个相册会按预期显示 3 张图片，但所有其他相册都没有图片.

This does limit the number of images to 3 but it limits the total count of images to 3 but I want to limit each album to 3 images. So the first album will show 3 images as expected but all the other albums have no images.

我尝试向我的模型中添加一个新方法，如下所示:

I have tried adding a new method to my model like so:

public function limitImages()
{
    return $this->hasMany('AppImage')->limit(3);
}

我在控制器中调用它:

Album::with('limitImages')->get();

但这根本不限制返回的图像数量

But this doesn't limit the image count returned at all

推荐答案

我觉得你会很快遇到 N+1 问题，试图实现这一点.只需在它返回的集合中执行此操作:

I feel you'd quickly run into an N+1 issue trying to accomplish this. Just do it in the collection that it returns:

Album::with('images')->get()->map(function($album) {
    $album->setRelation('images', $album->images->take(3));
    return $album;
});

这篇关于Laravel Eloquent 关系的限制结果的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！