Symfony3 Fetching data from entities with ManyToMany association - symfony

Question

I have a problem with ManyToMany association. I cant't figure out how to fetch data from database.
I have 2 entities - Teacher and Subject.
Class Subject
/**
*
* #ORM\ManyToMany(targetEntity="Teacher", mappedBy="subjects")
*/
private $teachers;
public function __construct() {
$this->teachers = new ArrayCollection();
}
/**
* Add teacher
*
* #param \AppBundle\Entity\Teacher $teacher
*
* #return Subject
*/
public function addTeacher(\AppBundle\Entity\Teacher $teacher)
{
$this->teachers[] = $teacher;
return $this;
}
/**
* Remove teacher
*
* #param \AppBundle\Entity\Teacher $teacher
*/
public function removeTeacher(\AppBundle\Entity\Teacher $teacher)
{
$this->teachers->removeElement($teacher);
}
/**
* Get teachers
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getTeachers()
{
return $this->teachers;
}
And entity Teacher
Class Teacher
/**
*
* #ORM\ManyToMany(targetEntity="Subject", inversedBy="teachers")
*/
private $subjects;
public function __construct()
{
$this->subjects = new ArrayCollection();
}
/**
* Add subject
*
* #param \AppBundle\Entity\Subject $subject
*
* #return Teacher
*/
public function addSubject(\AppBundle\Entity\Subject $subject)
{
$this->subjects[] = $subject;
return $this;
}
/**
* Remove subject
*
* #param \AppBundle\Entity\Subject $subject
*/
public function removeSubject(\AppBundle\Entity\Subject $subject)
{
$this->subjects->removeElement($subject);
}
/**
* Get subjects
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getSubjects()
{
return $this->subjects;
}
All i want to do is fetch all information from Teacher + Subjects associated with them.
How should looks like my controller to do this?
I try do this by
$teacher = $this->getDoctrine()->getRepository(Teacher::class)->findAll();
return $this->render('admin/adminDashboard.html.twig', [
'teachers' => $teacher]);
But i still got errors

Answer 1

First, my advice is to change your $teacher variable to $teachers as
findAll() method returns an array so you have to iterate through it. In your controller:
foreach($teachers as $teacher) { // Here you have $teacher and you can do $teacher->getSubjects() }
In your twig template:
{% for teacher in teachers %}
{{ dump(teacher) }}
{% endfor %}
If that doesnt work, let us know what kind of errors do you get.
This is all assuming that you have entries inside your database, or from wherever you're fetching your entities.

Answer 2

if {% for t in teachers %}{{dump(t.subjects.count)}}{% endfor %} worked, it means the data is there.
If you mean {{teacher.subjects}} throws error: An exception has been thrown during the rendering of a template ("Catchable Fatal Error: Object of class Doctrine\ORM\PersistentCollection could not be converted to string. Well in case you have never seen this error before, take a close read:
Object of class Doctrine\ORM\PersistentCollection refers to subjects, which as a collection that it is, cannot be just thrown into an html tag like a string.
Depends on how you want to present your data but the very basics would be:
{% for t in teachers %}
<tr>
{% for s in t.subjects %}
<td>s.getName</td>
{% endfor %}
</tr>
{% endfor %}
assuming subject entity has a property name and a getter for it. Hope you get the gist.
let me know