Scan pivot table for two identical values - laravel

Question

I have this pivot table:
+----+---------+-----------------+
| id | user_id | conversation_id |
+----+---------+-----------------+
| 1 | 2 | 48 |
+----+---------+-----------------+
| 2 | 1 | 48 |
+----+---------+-----------------+
I am trying to find a way to detect if two users are in the same conversation, and if they are, return the conversation. Someting like:
Conversation::with([1, 2]); // should return conversation 48
My Conversation class looks like this:
class Conversation extend Eloquent {
public function users() {
return $this->belongsToMany('User');
}
public function messages(){
return $this->hasMany('Message');
}
}
So far I have below code, but it is clumsy and very ineffective, and thought that there must exists some cleaner Laravel way:
class Conversation {
public static function user_filter(Array $users) {
$ids = array();
foreach ($users as $user)
$ids[$user->id] = $user->id;
sort($ids);
foreach (self::all() as $conversation){ // loop through ALL conversations (!!!)
$u_ids = $conversation->users->lists('id');
sort ( $u_ids );
if ($u_ids === $ids)
return $conversation;
}
return null;
}
}
Usage:
Conversation::user_filter([User::find(1), User::find(2)]); // returns conversation 48
Any ideas?

Answer 1

Let's first look at how you can actually retrieve the result without having too loop trough all kind of arrays...
You can use the whereHas function to filter a relationship. We can apply conditions and if they are met for the related records of a model, it will be included in the result.
$conversations = Conversation::whereHas('users', function($q){
$q->where('user_id', 1);
})->get();
So that's for one user. For two or more users it's basically the same. You just need to chain whereHass
$conversations = Conversation::whereHas('users', function($q){
$q->where('user_id', 1);
})
->whereHas('users', function($q){
$q->where('user_id', 2);
})->get();
Now this isn't very elegant. You can create a query scope to do all the work for you and keep the controller code clean. In Conversation
public function scopeWithUsers($query, array $userIds){
foreach($userIds as $id){
$query->whereHas('users', function($q) use ($id){
$q->where('user_id', $id);
});
}
return $query;
}
Usage:
$conversations = Conversation::withUsers([1,2])->get();
$conversations = Conversation::withUsers([1,2,3,4])->get();
$conversations = Conversation::withUsers([1])->get();
If it should only be one anyways use first() instead of get()

Answer 2

Something like this should work.
class Conversation {
public static function user_filter(Array $users) {
$ids = array();
foreach ($users as $user) {
$ids[] = $user->id;
}
return self::select("conversation_id")->whereIn("user_id", $ids)->groupBy("conversation_id")->havingRaw("count(*) = " . count($ids))->get();
}
}

Answer 3

Get all conversations with given users.
Conversation::whereHas('users', function($query) use ($userids) {
$query->whereIn('user_id', $userids);
})->get();
If you need get special one, you can:
Conversation::whereHas('users', function($query) use ($userids) {
$query->whereIn('user_id', $userids);
})->whereId($id)->first();