Laravel - How to prevent delete when there is dependent field - laravel

Question

In my Laravel-5.8 project, I have these models
HrGradeLevel
class HrGradeLevel extends Model
{
protected $table = 'hr_grade_levels';
protected $fillable = [
'grade_level_code',
'grade_level_name',
'description',
];
public function designation(){
return $this->hasMany('App\Models\Hr\HrDesignation');
}
public function employee(){
return $this->hasMany('App\Models\Hr\HrEmployee');
}
}
HrDesignation
class HrDesignation extends Model
{
protected $table = 'hr_designations';
protected $fillable = [
'designation_name',
'grade_level_id',
];
protected $casts = [];
public function gradelevel()
{
return $this->belongsTo('App\Models\Hr\HrGradeLevel','grade_level_id');
}
}
HrEmployee
class HrEmployee extends Model
{
protected $table = 'hr_employees';
protected $fillable = [
'first_name',
'last_name',
'grade_level_id',
];
protected $casts = [];
public function gradelevel()
{
return $this->belongsTo('App\Models\Hr\HrGradeLevel','grade_level_id');
}
}
HrDesignation and HrEmployee has foreign key grade_level_id that is derived from HrGradeLevel
HrGradeLevelController
public function destroy(Request $request, $id)
{
$grade = HrGradeLevel::find($id);
$grade->delete();
Session::flash('success', 'Grade Level deleted successfully.');
return redirect()->route('hr.grade_level.index');
}
From the Controller above, the user can delete HrGradeLevel row.
Using Laravel, before the user is allowed to delete I want the application to check HrDesignation and HrEmployee, if any of them have data in grade_level_id, I want the application to display a message and it shouldn't allow delete.
How do I achieve this?
Thank you.

Answer 1

You have 2 options:
Use foreign key constraints on your migrations and MySQL will prevent deleting a record if foreign key is used on other tables/records by default:
public function destroy(Request $request, $id)
{
$grade = HrGradeLevel::find($id);
try {
$grade->delete();
}
catch (\Illuminate\Database\QueryException $e) {
if ($e->getCode() == 23000)
{
//SQLSTATE[23000]: Integrity constraint violation
abort('Resource cannot be deleted due to existence of related resources.');
}
}
Session::flash('success', 'Grade Level deleted successfully.');
return redirect()->route('hr.grade_level.index');
}
Check existence of your relationships before deleting:
public function destroy(Request $request, $id)
{
$grade = HrGradeLevel::find($id);
if ($grade->designation()->exists()
|| $grade->employee()->exists())
{
abort('Resource cannot be deleted due to existence of related resources.');
}
$grade->delete();
Session::flash('success', 'Grade Level deleted successfully.');
return redirect()->route('hr.grade_level.index');
}