Agfdhyk

Suppose I have a Course model like this :

class Course extends Model

{    

        public $primaryKey = 'course_id';



        protected $appends  = ['teacher_name'];



        public function getTeacherNameAttribute ()

        {

            $this->attributes['teacher_name'] = $this->teacher()->first()->full_name;

        }



        public function teacher ()

        {

            return $this->belongsTo('AppUser', 'teacher', 'user_id');

        }

}

And in the other hand there is a User model like this :

class User extends Authenticatable

{



        public $primaryKey = 'user_id';



        protected $appends = ['full_name'];



        public function getFullNameAttribute ()

        {

            return $this->name . ' ' . $this->family;

        }



        public function course ()

        {

            return $this->hasMany('AppCourse', 'teacher', 'user_id');

        }



}

As you can see there is a hasMany relationship between those.

There is an full_name accessor in User model.

Now I want to add a teacher_name accessor to Course model that uses it's teacher relations and gets full_name of teacher and appends to Course always.

In fact I want whenever call a Course model, it's related teacher name included like other properties.

But every time , when call a Course model , I got this error :

exception 'ErrorException' with message 'Trying to get property of non-object' in D:wampwwwlms-apiappCourse.php:166

That refers to this line of Course model :

$this->attributes['teacher_name'] = $this->teacher()->first()->full_name;

I do not know how can I solve that and what is problem exactly.

the right way to do this is:

COURSE

public function setTeacherNameAttribute ()

{

    $this->attributes['teacher_name'] = $this->teacher->full_name;

}

$this->attributes['teacher_name'] = $this->teacher()->first()->full_name;

Should be

$this->attributes['teacher_name'] = $this->teacher->full_name;

First thing is that you want to reference the relationship, so loose the brackets (), and because the relationship is belongsTo, you will have one user / teacher returned. So you don't need the first().

We haven't seen your fields but probably you will have to change:

return $this->belongsTo('AppUser', 'teacher', 'user_id');

to

return $this->belongsTo('AppUser', 'foreign_key', 'other_key');

where foreign_key and other_key are the primary keys that you need to make the join on.

Check this link from the documentation for reference:
https://laravel.com/docs/5.4/eloquent-relationships#one-to-many-inverse

This error is only object data to array use or array data to object data use.

example::

$var->feild insted of $var[feild]

$var[feild] insted of $var->feild