laravel中多对多关系如何正确检索数据？

Question

I have a many to many relationship with a pivot table.

goods

id | title | ...

tags

id | title | ...

good_tag

id | good_id | tag_id | ...

How correctly retrieve all goods and their tags in laravel?

Thanks

Answer 1

Ok, first lets write the relationships in your models:

Good Model( representing goods table)

public function getTags()
{
    return $this->belongsToMany('Tag','good_tag','good_id','tag_id');
}

Tag Model (representing tags table), this is reverse relationship to get goods for a specific tag

---

public function getGoods()
{
    return $this->belongsToMany('Good','good_tag','tag_id','good_id');
}

---

Now to retrieve all goods and their tags here's the code:

    $goods=Good::All();  
    foreach($goods as $good)
    {
        echo $good->title;
        echo "Tags: ";
        foreach($good->getTags as $tag)
        {
            echo $tag->title." ";
        }

    }

Answer 2

With Eager Loading

$goods = Good::with('tags')->get();

foreach ($goods as $good) {
    // each goods
    echo $good->title;

    foreach ($good->tags as $tag) {
        // each tag for that goods
        echo $tag->title;
    }
}

Each returned Good model will have its collection of Tags attached.

Docs - Eloquent - Eager Loading