How to do the following with doesn't have or other optimized way in laravel

问题

I have a thread which gave the answer but later on I found that I was getting limitations: how to get list of users who are not under belongsToMany relation under a table in laravel?

so creating a new thread where I do have an answer but now how can I optimize the same with any prebuild functions like doesntHave or something entirely else.

below is the code which gives me the list of users who are under a group and not assigned any task. one group can have multiple tasks so only users where the task is not assigned needs to be listed.

$gid = $task->group_id;
$MembersList =  $task->members;
$group_subscribers = Group::with(['subscribedUsers' => function($q){
    $q->select('id');
}])->whereId($gid)->get();
$group_subscribers = $group_subscribers[0]->subscribedUsers->pluck('id')->toArray();
$alreadyMembers =  DB::table('task_user')->select('user_id as id')->whereIn('user_id', $group_subscribers)->pluck('id')->toArray();
$finalList =  array_diff($group_subscribers, $alreadyMembers);
$users = User::whereIn('id', $finalList)->get();
return $users;

any way to improve the above code?

回答1:

I guessed Users and Tasks was in a many to many relationship. For my optimisation to work, i added the following relationship to the User model, this is gonna be used when we filter the subscribed users.

public class Users {
    public function tasks() {
        return $this->belongsToMany(Task::class);
    }
}

Basically the implementation is filtering all the subscriber users and checking if they have tasks, since tasks is a relationship it returns a Collection and isNotEmpty() is used for that reason.

$groupId = $task->group_id;

$group = Group::with(['subscribedUsers.tasks'])->find($groupId));

$withoutTasks = $group->subscribedUsers->filter(function ($user) {
    return $user->tasks->isNotEmpty();
} );

return $withoutTasks;

It is a rule of thumb to avoid DB:: methods and you should be able to go to model to model, instead of making queries from getting from one model to another.

来源：https://stackoverflow.com/questions/59284155/how-to-do-the-following-with-doesnt-have-or-other-optimized-way-in-laravel