Relationship condition if user is logged in

I want to create a relationship that checks if a user has liked a post. In order to do this, the relationship needs to check if the user is logged in, and then use their user_id to get the like record. Something like:

public function userLike() {
    if (Auth::check()) return $this->hasOne('App\Like')->where('user_id', Auth::user()->id);
}

However, this doesn't work. Additionally, if the user is not logged in and this relationship is called (which it is by default), it will return an error.

What is the proper way of doing this?

via Chebli Mohamed