Call to undefined relationship on model laravel using scope - php

Question

I'm trying to get 5 posts for each category so I did a little search and ends up here Getting n Posts per category
But I'm getting a weird Call to undefined relationship on model when using with scope but it all works fine If I don't use a scope. Here is the Category Model
//Relationship with posts
public function posts(){
return $this->hasMany('App\Post');
}
scopeNPerGroup
public function scopeNPerGroup($query, $group, $n = 10)
{
// queried table
$table = ($this->getTable());
// initialize MySQL variables inline
$query->from( \DB::raw("(SELECT #rank:=0, #group:=0) as vars, {$table}") );
// if no columns already selected, let's select *
if ( ! $query->getQuery()->columns)
{
$query->select("{$table}.*");
}
// make sure column aliases are unique
$groupAlias = 'group_'.md5(time());
$rankAlias = 'rank_'.md5(time());
// apply mysql variables
$query->addSelect(\DB::raw(
"#rank := IF(#group = {$group}, #rank+1, 1) as {$rankAlias}, #group := {$group} as {$groupAlias}"
));
// make sure first order clause is the group order
$query->getQuery()->orders = (array) $query->getQuery()->orders;
array_unshift($query->getQuery()->orders, ['column' => $group, 'direction' => 'asc']);
// prepare subquery
$subQuery = $query->toSql();
// prepare new main base Query\Builder
$newBase = $this->newQuery()
->from(\DB::raw("({$subQuery}) as {$table}"))
->mergeBindings($query->getQuery())
->where($rankAlias, '<=', $n)
->getQuery();
// replace underlying builder to get rid of previous clauses
$query->setQuery($newBase);
}
Calling Npergroup with relation
public function latestposts()
{
return $this->posts()->latest()->nPerGroup('category_id', 5);
}
Post Model Relationship
//Post belongs to Category
public function category(){
return $this->belongsTo('App\Category');
}
In my category controller I'm calling latestposts through
$categories = Category::with('latestposts')->get();
But I'm getting the error: Call to undefined relationship on model
What I want is:
Get the N number of posts per each category but I'm completely lost at this point. Any help would be appreciated
Reference:
Tweaking Eloquent relations – how to get N related models per parent ?

Answer 1

I am giving this answer based on your purpose that you want 5 posts per category.
So you have Category Model and Post Model.
And in Category Model you have relation with Post model like this
//Relationship with posts
public function posts(){
return $this->hasMany('App\Post');
}
And in Post Model you have relation with Category model like this
//Post belongs to Category
public function category(){
return $this->belongsTo('App\Category');
}
I show your question you have done SQL queries.
Instead of that, You can use two approaches
1) Give condition while eagar loading
$categories = Category::with(['posts' => function ($query) {
$query->orderBy('created_at', 'desc')->take(5);
}])->get();
Note: This approach will only work when you take only one result of parent child using first() method.
To get n number of posts per category Use this.
First, you can retrieve all categories with
$categories = Category::all();
Then you can use foreach loop and in all $category you have to give assign new attribute in it like here latestposts,
foreach ($categories as $category)
{
$category->latestposts = $category->posts()->orderBy('created_at','desc')->take(5)->get();
}
After this foreach loop you will get latest 5 posts in all categories.
Try this in your code and comment your queries and reviews.