Laravel 5.1：仅获取相关模型的记录

Question

I have three models:

• Category
• Post
• Comment

These are their implementations:

class Category extends \Eloquent {
    public function posts() {
        return $this->hasMany('Post');
    }
}


class Post extends \Eloquent {
    public function category() {
        return $this->belongsTo('Category');
    }
    public function comments() {
        return $this->hasMany('Comment');
    }
}

class Comment extends \Eloquent {
    public function post() {
        return $this->belongsTo('Post');
    }
}

Is it possible, using eloquent, to get a list (array or collection) of all the comments (and only the comments, without posts) related to a Category? (this means, given a category find all the related posts and then return all the related comments).

Thanks in advance!

Answer 1

Simply use hasManyThrough relation on your model Category :

class Category extends \Eloquent {
    public function posts() {
        return $this->hasMany(Post::class);
    }
    public function comments() {
        return $this->hasManyThrough(Comment:class,Post::class);
    }
}

After that, you can simply call $category->comments to have a Collection with all the comments related to a Category.

See https://laravel.com/docs/5.1/eloquent-relationships#has-many-through for extra information.

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