retrieve child object by evaluating grandchildren object in laravel - php

Question

I have 2 models, User and Conversation related to each other with a many-to-many relationship, many users to many conversations.
On my models I have:
User:
public function conversation() {
return $this->belongsToMany('App\Models\Conversation');
}
Conversation:
public function users() {
return $this->belongsToMany('App\Models\User');
}
So I could get the conversations a user has by : $user->conversation; and vice versa, retrieve the users a conversation has by $conversation->users, works like a charm. The problem is that I want a way to retrieve all users a certain user has made contact before, in few words, something like:
$user = User::find(1);
$talkedUsers = $user->conversation->user.
And also a way to check all the conversation user 'x' has made with user 'y' ('if any')
$userX = User::find(1);
$userY = 2;
$talkedUser = $userX->conversation->where('user.id', '=', $userY);
Obviously, the code above won't work. I wish to know if something like this is possible to accomplish without adding a complex raw query, I hope is possible only using only QueryBuilder.

Answer 1

The problem is that I want a way to retrieve all users a certain user
has made contact before,
$user->conversation is actually a collection of conversations, it is better to use plural i.e. $user->conversations. Then you can use higher order messages to deal with multiple objects at once. See https://laravel.com/docs/8.x/collections#higher-order-messages for more information
$users = $user->conversations->flatMap->users->unique('id');
flatMap combines multiple User collections retrieved from multiple Conversation objects into one collection of User objects then to remove duplicate users, you can use unique('id')
And also a way to check all the conversation user 'x' has made with
user 'y' ('if any')
First you should query all conversations from x then filter only conversations that have relationships with y.
$userX = User::find($x);
$conversations = $userX->conversations()
->whereHas('users', function($query) use ($y) {
$query->where('users.id', $y);
})
->get();