Retrieve related models using hasManyThrough on a pivot table - Laravel 5.7 - laravel

Question

I'm trying to retrieve related models of the same type on from a pivot table.
I have 2 models, App\Models\User and App\Models\Group and a pivot model App\Pivots\GroupUser
My tables are have the following structure
users
id
groups
id
group_user
id
user_id
group_id
I have currently defined relationships as
In app/Models/User.php
public function groups()
{
return $this->belongsToMany(Group::class)->using(GroupUser::class);
}
In app/Models/Group.php
public function users()
{
return $this->belongsToMany(User::class)->using(GroupUser::class);
}
In app/Pivots/GroupUser.php
public function user()
{
return $this->belongsTo(User::class);
}
public function group()
{
return $this->belongsTo(Group::class);
}
I'm trying to define a relationship in my User class to access all other users that are related by being in the same group. Calling it friends. So far I've tried this:
app/Models/User.php
public function friends()
{
return $this->hasManyThrough(
User::class,
GroupUser::class,
'user_id',
'id'
);
}
But it just ends up returning a collection with only the user I called the relationship from. (same as running collect($this);
I have a solution that does work but is not ideal.
app/Models/User.php
public function friends()
{
$friends = collect();
foreach($this->groups as $group) {
foreach($group->users as $user) {
if($friends->where('id', $user->id)->count() === 0) {
$friends->push($user);
}
}
}
return $friends;
}
Is there a way I can accomplish this using hasManyThrough or some other Eloquent function?
Thanks.

Answer 1

You can't do that using hasManyThrough because there is no foreign key on the users table to relate it to the id of the group_user table. You could try going from the user to their groups to their friends using the existing belongsToMany relations:
app/Models/User.php:
// create a custom attribute accessor
public function getFriendsAttribute()
{
$friends = $this->groups() // query to groups
->with(['users' => function($query) { // eager-load users from groups
$query->where('users.id', '!=', $this->id); // filter out current user, specify users.id to prevent ambiguity
}])->get()
->pluck('users')->flatten(); // massage the collection to get just the users
return $friends;
}
Then when you call $user->friends you will get the collection of users who are in the same groups as the current user.