Laravel雄辩得到关系计数

Question

我使用Laravel 5.3.

我有2张桌子:

Articles
---------
id
cat_id
title

和

Category
---------
id
parent_id
title

我在模特中定义了我的关系:

// Article model
public function category()
{
    return $this->belongsTo(Category::class);
}

// Category model
public function children() 
{
    return $this->hasMany(Category::class, 'parent_id', 'id');
}   

有没有一种简单的方法可以使用Eloquent来列出包含文章数量的类别.困难在于我想将类别分组在哪里id_parent = 0,即我想仅显示具有儿童文章数量的父类别.

我试过这样的事情:

    $category = new \App\Models\Category();
    $categoryTable = $category->getTable();

    return $category->leftJoin('article', 'article.cat_id', '=', 'category.id')
        ->whereIn('article.cat_id', function($query)
            {
                $query->select('cat_id')
                    ->from('categories')
                    ->where('categories.parent_id', ???)
                    ->orWhere($this->tableName .'.cat_id', $id);
            })
        ->groupBy('cat_id');

但我迷路了......

Answer 1

你可以使用withCount().它有5.3版本

有关雄辩访问的更多信息:https://laravel.com/docs/5.3/eloquent-relationships

Answer 2

您可以使用hasManyThrough()Eloquent方法获取所有儿童文章，然后将文章计数添加到一个漂亮的小吸气器中。我将吸气剂添加到$appends模型上的数组中，以帮助在Tinker输出中进行说明。

class Category extends Model
{

    protected $appends = [
        'articleCount'
    ];

    public function articles()
    {
        return $this->hasMany(Article::class);
    }

    public function children()
    {
        return $this->hasMany(Category::class, 'parent_id');
    }

    public function childrenArticles()
    {
        return $this->hasManyThrough(Article::class, Category::class, 'parent_id');
    }

    public function getArticleCountAttribute()
    {
        return $this->articles()->count() + $this->childrenArticles()->count();
    }
}

这是Tinker的输出：

Psy Shell v0.8.0 (PHP 7.0.6 — cli) by Justin Hileman
>>> $cat = App\Category::first();
=> App\Category {#677
     id: "1",
     name: "Cooking",
     parent_id: null,
     created_at: "2016-12-15 18:31:57",
     updated_at: "2016-12-15 18:31:57",
   }
>>> $cat->toArray();
=> [
     "id" => 1,
     "name" => "Cooking",
     "parent_id" => null,
     "created_at" => "2016-12-15 18:31:57",
     "updated_at" => "2016-12-15 18:31:57",
     "articleCount" => 79,
   ]
>>> 

如果要将类别查询限制为那些子项中包含文章的查询，则可以使用以下has()方法：

Category::has('children.articles')->get();

以下是有关has()方法的更多信息：

https://laravel.com/docs/5.3/eloquent-relationships#querying-relationship-existence

和hasManyThrough()方法：

https://laravel.com/docs/5.3/eloquent-relationships#has-many-through

Answer 3

Define a articles() relation in your Category model as:

public function articles() 
{
    return $this->hasMany(Article::class, 'cat_id');
}

Then you can try it as:

Category::where('parent_id', 0)->withCount('articles')->get();