Laravel - How to make students not to score beyond the max mark - laravel

Question

I am using Laravel-5.8 for a web application project. In the project I have these tables:
class SubjectCategory extends Model
{
protected $table = 'subject_categories';
protected $fillable = [
'name',
'parent_id',
'max_mark',
];
public function children()
{
return $this->hasMany('App\Models\SubjectCategory', 'parent_id');
}
public function exams()
{
return $this->hasMany('App\Models\Exam');
}
}
class Exam extends Model
{
protected $table = 'exams';
protected $fillable = [
'subject_category_id',
'student_id',
'student_mark',
'subject_name',
];
public function subjectcategory()
{
return $this->belongsTo('App\Models\SubjectCategory','subject_category_id');
}
}
SubjectCategory is an hierarchical table. Only the parent have the max_mark
Here is the Controller
public function create()
{
$categories = SubjectCategory::with('children')->whereNull('parent_id')->get();
return view('exams.create')
->with('categories', $categories);
}
public function store(StoreExamRequest $request)
{
$exam = new Exam();
$exam->stubject_category_id = $request->stubject_category_id;
$exam->student_id = $student_id;
$exam->student_mark = $request->student_mark;
$exam->save();
return redirect()->route('exams.index');
}
view blade
<div class="row">
<div class="col-md-12">
<!-- general form elements -->
<div class="card card-secondary">
<form method="POST" action="{{route('exams.store')}}">
#csrf
<div class="card-body">
<div class="form-body">
<div class="row">
<div class="col-12 col-sm-6">
<div class="form-group">
<label class="control-label"> Subject Category:<span style="color:red;">*</span></label>
<select id="subject_category" class="form-control" name="subject_category_id">
<option value="">Select Subject Category</option>
#foreach ($categories as $category)
<option disabled="disabled" value="{{ $category->id }}" {{ $category->id == old('category_id') ? 'selected' : '' }}>{{ $category->name }}</option>
#if ($category->children)
#foreach ($category->children as $child)
<option value="{{ $child->id }}" {{ $child->id == old('category_id') ? 'selected' : '' }}> {{ $child->name }}</option>
#endforeach
#endif
#endforeach
</select>
</div>
</div>
<div class="col-12 col-sm-6">
<div class="form-group">
<label class="control-label"> Subject Name:<span style="color:red;">*</span></label>
<input type="text" name="subject_name" placeholder="Enter Subject Name here" class="form-control">
</div>
</div>
<div class="col-12 col-sm-4">
<div class="form-group">
<label class="control-label"> Mark Obtained:</label>
<input type="number" name="student_mark" placeholder="Enter Mark Obtained here" class="form-control">
</div>
</div>
</div>
</div>
</div>
<!-- /.card-body -->
<div class="card-footer">
<button type="submit" class="btn btn-primary">Save</button>
</div>
</form>
</div>
<!-- /.card -->
</div>
<!--/.col (left) -->
</div>
Subjects are categorized. From SubjectCategory, the parent subject have sub subjects as children. Only the Parent Subject Category have the Maximum Obtainable Score (Max Mark).
From the Exam (subject_category_id) dropdownlist contains all the children fields from subject_categories. What I want to achieve is this:
When Subject Category is selected from the dropdownlist, the system goes to the exams table. It displays total student_mark based on student_id and subject_category_id.
In each subject, the student accumulated mark cannot be more than the max_mark in the parent subject_category.
When the user tries to enter data into student_mark text field, the application adds the value in the text field to the student aggregate. If the result is more than the max_mark in subject_categories (SubjectCategory) based on the parent max_mark, then an error message is displayed.
How do I achieve this?
Thank you.

Answer 1

This is achievable in a couple of different ways; you could use validation to prevent someone entering a value over the max mark, or if they do enter a value over the max mark then you just silently reduce it back to the max mark.
I would suggest you take the validation approach and to do this you would need to use a custom validation rule.
You can read up on the documentation for how to create one (https://laravel.com/docs/5.8/validation#custom-validation-rules) but the implementation might look a little something like this:
// Inside a form request (or you could use inline validation in your controller
'student_mark' => [new NotOverMaxMark($this->input('subject_category_id'))]
Then for the rule itself might look a little something like this:
<?php
namespace App\Rules;
use App\SubjectCategory;
use Illuminate\Contracts\Validation\Rule;
class NotOverMaxMark implements Rule
{
private $subjectCategory;
public function __construct($subjectCategoryId)
{
$this->subjectCategory = SubjectCategory::findOrFail($subjectCategoryId);
}
public function passes($attribute, $value)
{
return $value <= $this->subjectCategory->max_mark;
}
public function message()
{
return 'The :attribute must not be higher than the max mark.';
}
}
The above is an example of how you might do this, you may need to tweak the imports or implementation to your needs.