Relationship hasManyThrough in Laravel? - laravel

Question

I have three models: User, Category, Announcement.
User model:
public function categories()
{
return $this->belongsToMany("App\Category");
}
public function announcements()
{
return $this->hasManyThrough('App\Announcement', 'App\Category');
}
Category model:
public function announcements()
{
return $this->belongsToMany('App\Announcement');
}
Announcement model:
public function categories()
{
return $this->belongsToMany('App\Category');
}
I need to select all announcements through user_categories table.
For this I do:
$res = User::where("id", 1)->with("announcements")->get();
dd($res);
In result I get SQL error:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'announcements.category_id' in 'on clause' (SQL: select `announcements`.*, `categories`.`user_id` from `announcements` inner join `categories` on `categories`.`id` = `announcements`.`category_id` where `categories`.`user_id` in (1) and `announcements`.`deleted_at` is null)
Why Laravel does try to search ``announcements.category_id` in table?
In conclusion I need to get all announcements on categories which user subscribed.
Table Database structure:
Users
id | name
Announcements
id | name
categories
category_id | announcement_id
users_categories
category_id | user_id
So, I need to get all announcements through table users_categories where there are relation this table with categories that is belong to announcement table.

Answer 1

You cannot eager load this relationship because
To perform this query, Eloquent inspects the foreign key on the intermediate table.
Thus the error
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'announcements.category_id'
Because HasManyThrough() looks for the relationship in the specified model table.
I would suggest you look at this thread:
https://laravel.io/forum/05-21-2014-problem-with-eloquents-hasmanythroughs-query
They show you how to write your own query to do that. An example would be, in the user model do
public function getAnnouncements() {
$announcements = [];
foreach( $this->categories as $category ) {
foreach( $category->announcements as $annoucement ) {
if ( !isset($announcements[$annoucement->id]) ) { //avoid duplicates
$annoucements[$announcement->id] = $announcement;
}
}
}
}
The nested foreach will give all announcement belonging to a category that related to a user.
Improving the function
public function getAnnouncements() {
$announcements = new Collection();
foreach( $this->categories as $category ) {
$announcements->collect($category->announcements);
}
}