与用户条件的关系

Question

I have a follow system that works like Twitter's follow (you follow other people and get updates from them).

I have this relationship set in my User.php model:

public function follows()
{
    return $this->hasMany('App\Follow');
}

This obviously gets all records of users who follow this person.

However, when displaying the person's profile page, I want to get a relationship that checks if a follow record exists given the user ID.

Something like:

public function userFollow()
{
    return $this->hasOne('App\Follow')->where('user_id', Auth::user()->id);
}

So now my profile page query looks like this:

$user = User::where('username', $username)
    ->with('userFollow')
    ->first();

This works as long as the user is logged in. If the user isn't logged in, the page gives me this error:

ErrorException in User.php line 28: Trying to get property of non-object

How do I fix this? What is the proper way of using conditions in relationships?

Answer 1

This is because if user is logged out then Auth::user() is null, because user session has ended. Auth::user() is no more object, so you can't get the id from a null object.

Here you can do something like that

public function userFollow()
{
  $userId = Auth::user() ? Auth::user()->id : $this->id; 
  return $this->hasOne('App\Follow')->where('user_id', $userId);
}

then it will not look for authenticated user, it will just get the particular user table's id.

Answer 2

The proper way of using conditions in relationships is using Constraining eager loads

public function userFollow()
{
    return $this->hasOne('App\Follow');
}

And,

if(Auth::check())
{
       $user = User::where('username', $username)
             ->with(['userFollow'=>function($query)
                {
                    $query->where('user_id', Auth::user()->id);
                }]);
             ->first();
}