在laravel查询中与关系堆栈

Question

I need your help. I have this query but I am getting trouble

I have these two tables:

users
---------------------
 id | name | surname
---------------------

users_ratings 
-------------------------------------
 id | user_id | customer_id | rating
-------------------------------------

Not every user has a rating.

I am trying to show on a view in Laravel every user and it's rating.

$users=User::where('role','=','4')->paginate(8);
$data = array();
foreach ($users as $user)
{
    $ratings = UserRating::where('user_id', $user->id)->get();
    $nr = UserRating::where('user_id',  $user->id)->count();
    $sum = 0;


        foreach ($ratings as $rate) {
            if ($rate->rating != "") {
                $rating = $rate->rating;
                $sum = $sum + $rating;

            }
        }

        if ($nr == 0) {
            $avg = 0;
        } else {
            $avg = ($sum / $nr);
        }

    }
    else {

        $avg=0;
    }
        $object = [
            'id' => $user->id,
            'rating' => number_format($avg, 3, '.', ','),
            'user'=>$user
        ];

        array_push($data, $object);

       return view('pages.users', ['data' => $data]);

Now I am showing in view:

@foreach($data as $d)
    {{$d->id}}
    {{$d->rating}]
    {{$d->user->name}}
@endforeach

I know that something is wrong here. It shows

"Trying to get property 'id' of non-object....

Answer 1

You should try this:

@foreach($data as $d)
{{$d['id']}}
{{$d['rating']}}

@endforeach

OR

@foreach($data as $key => $d)
    {{$d[$key]->id}}
    {{$d[$key]->rating}]
    {{$d[$key]->user->name}}
@endforeach

Updated Answer

@foreach($data as $key => $d)
  @foreach($d as $rsltDetails)
    {{$rsltDetails['id']}}
    {{$rsltDetails['rating']}}
  @endforeach
@endforeach

Answer 2

There are many things wrong here.

First, you have an n+1 query. You are fetching the users and inside the loop for each user, you are performing 2 additional queries.

$users = User::where('role','=','4')->paginate(8);

foreach ($users as $user) {
    $ratings = UserRating::where('user_id', $user->id)->get();
    $nr = UserRating::where('user_id',  $user->id)->count();
    $sum = 0;
    ...
}

Solution:

This code will execute only two queries.

// I am assuming the relation name between User and UserRating is ratings
$users = User::with('ratings')->where('role','=','4')->paginate(8);

return view('pages.users', compact('users));

In your view, you can easily print the values

@foreach($users as $user)
    {{ $user->id }}
    {{ number_format($user->ratings->avg('rating'), 3, '.', ',') }}
    {{ user->name }}
@endforeach

Answer 3

Doing it that way is not a scalable solution and you will face the N+1 problem. I would suggest the following.

First, in your App\\User model, define your relationship with App\\UserRating :

use App\UserRating; 

public function ratings()
{
    return $this->hasMany(UserRating::class); 
}

Then, define your inverse relationship in App\\UserRating

use App\User; 

public function user()
{
    return $this->belongsTo(User::class);
}

Finally, you could simplify your loop like this:

$users = User::where('role','=','4')
    ->with('ratings') // eager-load ratings
    ->paginate(8);

$results = []; 

foreach($users as $user) {
    // To access ratings you would do 
    // foreach($user->ratings as $rating) { }

    // To get the count you would do 
    // $user->ratings->count(); 
}

In your blade file, you could just do this:

@foreach($users as $user)
    {{ $user->id }}
    {{ number_format($user->ratings->avg('rating'), 3, '.', ',') }}
@endforeach

Doing it this way will solve your N+1 problem and leverages Laravel's Collections to make everything a little bit cleaner as well :)