Property [students] does not exist on this collection instance - php

Question

So i have relationship declared on the parents Model as
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Parents extends Model
{
protected $fillable = [
'firstName',
'middleName',
'lastName',
'phoneNumber',
'gender',
];
public function students(){
return $this->belongsToMany('App\Student','parent_student','parentId','studentId');
}
}
with the anchor table parent_student and a students table with the column classId. here is the students model
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Student extends Model
{
//
protected $fillable = [
'firstName',
'middleName',
'lastName',
'regNo',
'gender',
'dob',
'classId',
];
public function parents(){
return $this->belongsToMany('App\Parents','parent_student','studentId','parentId');
}
public function classes()
{
return $this->belongsTo('App\Classes','classId');
}
}
what i am tring to achieve is to get the email addresses for parents with students in one class eg class 1, which i pass the classId from a dropdown select in a form on the view to the controller.
Here is my controller.
public function submitEmail(Request $request)
{
$validatedData = $request->validate([
'class' => 'required|integer',
'message' => 'string|max:255',
'subject' => 'string|max:255',
]);
$class = $request->input('class');
$message = $request->input('message');
$subject = $request->input('subject');
$parents = Parents::all();
$parents = Parents::where($parents->students->classId,"=",$class)->get();
die($parents);
}
I am fairly new to laravel and this is the far i have gone so far.Any suggestions would be much appreciated.(I am using laravel 5.6)

Answer 1

This line
$parents->students
is where your problem is. $parents is a Collection (array) of Parents models, not a single Parents1 model. To get a single classId, you need to use a Loop:
foreach($parents AS $parent){
... // Should be able to access $parent->students without issue;
}
Next, you're trying to access ->classId of $parent->students, which is the same issue. $parent->students is a Collection, and not a single Student2 model. You'd need another loop to get the classId:
foreach($parents AS $parent){
foreach($parent->students AS $student){
... // Should be able to access `$student->classId` without issue
}
}
But, this still doesn't solve your core issue. It's important to know when you're accessing a Collection vs a single Model, so keep that in mind.
All of that aside, it sounds like you're trying to get all the Parents of Students in Class of $class (passed from your <form>). To accomplish this, you can use ->whereHas(), as below:
$parents = Parents::whereHas("students", function($query) use($class){
$query->where("classId", "=", $class);
})->with(["students" => function($query) use($class){
$query->where("classId", "=", $class);
}])->get();
What this does, is queries the parents table for any student records that have a class with an id of $class.
Note that whereHas and with contains the same subquery to constrain and eager-load each Parents collection of Students to what's required.
Sidenote: Your classes() relationship on Student has an issue. Since it's a belongsTo() method, it should be class() (singular), as $student->classes would only return a single Class model.
1 Pay attention to naming conventions. Parents should be Parent; Model names are singular.
2 You named the Student Model right, so be consistent.

Answer 2

Try this query:
$parents = Parents::with(['students' => function($query) use ($class){
$query->where('classId',$class);
}])->get();
Instead of:
$parents = Parents::where($parents->students->classId,"=",$class)->get();
Then instead of die($parents) use dd($parents)