accessing data from a pivot table in laravel - php

Question

I am having trouble accessing data from an extra column in a pivot table.
I have two models (which are part of a larger application for managing grades in a k-12 school) - Grado and Subject. Grado refers to the grade, i.e first grade, second grade, etc. I want the administrator to be able to associate subjects to a grade level in a given year.
The mysql pivot table grado_subject contains:
id_grado_subject
year_grado_subject //year - column I want to access
grados_id_grados //foreign key id of grado
subjects_id_subjects //foreign key id of subject
created_at
updated_at
The Grado model:
<?php
use Illuminate\Auth\UserTrait;
use Illuminate\Auth\UserInterface;
use Illuminate\Auth\Reminders\RemindableTrait;
use Illuminate\Auth\Reminders\RemindableInterface;
class Grado extends Eloquent implements UserInterface, RemindableInterface {
use UserTrait, RemindableTrait;
protected $table = 'grados';
protected $primaryKey = "id_grados";
protected $fillable = array('name_grados');
public static $rules = array(
);
public function subject()
{
return $this->belongsToMany('Subject','grado_subject','grados_id_grados','subjects_id_subjects')
->withPivot('year_grado_subject')
->withTimestamps();
}
public function groups()
{
return $this->hasMany('Group','id_grados','grados_id_grados');
}
}
The Subject Model:
<?php
use Illuminate\Auth\UserTrait;
use Illuminate\Auth\UserInterface;
use Illuminate\Auth\Reminders\RemindableTrait;
use Illuminate\Auth\Reminders\RemindableInterface;
class Subject extends Eloquent implements UserInterface, RemindableInterface {
use UserTrait, RemindableTrait;
protected $table = 'subjects';
protected $primaryKey = "id_subjects";
protected $fillable = array('engSpanExtra_subjects', 'name_subjects','IntGrade_subjects');
public static $rules = array(
'name_subjects' => 'required',
'engSpanExtra_subjects' => 'required',
'IntGrade_subjects'=> 'required'
);
public function grado()
{
return $this->belongsToMany('Grado','grado_subject','subjects_id_subjects','grados_id_grados')
->withPivot('year_grado_subject')
->withTimestamps();
}
public function teacher()
{
return $this->belongsToMany('Teacher','subject_teacher','subjects_id_subjects','teachers_id_teachers');
}
}
In the GradoController:
class GradoController extends \BaseController {
public function index()
{
$grados = Grado::find(1);
$years = $grados->pivot->year_grado_subject;// line I get error on
return $years;
$grados->toarray();
return View::make('grados.index',compact('grados', 'years'));
}
When I try to retrieve all the years associated with a grade_subject I get the error: Trying to get property of a non-object.
Any help would be greatly appreciated!

Answer 1

public function subject()
{
return $this>belongsToMany('Subject','grado_subject','grados_id_grados','subjects_id_subjects')
->withPivot('year_grado_subject')
->withTimestamps();
}
You have some syntax errors I'm seeing in the above. First you have $this>belongsToMany which should be $this->belongsToMany
Another thing you might check is $this->belongsToMany('Subject', ...) You aren't including your Student model in a use clause therefore you have to use a fully qualified reference and it should be $this->belongsToMany('\Student', ...).
You have the same syntax errors in your Grado model. Check these first and see if your error is solved.

Answer 2

The pivot attribute is generated by the belongsToMany relationship, therefore it exists on the objects loaded by that relationship (subjects), not the primary object (grado).
For example:
// primary object is grado
$grado = Grado::find(1);
// loop through related subjects
foreach($grado->subject as $subject) {
// pivot attribute exists on related subject
echo $subject->pivot->year_grado_subject;
}
Or, if you were going the inverse way:
// primary object is subject
$subject = Subject::find(1);
// loop through related grados
foreach($subject->grado as $grado) {
// pivot attribute exists on related grado
echo $grado->pivot->year_grado_subject;
}