Ggtcf

I want to delete a model but it might have related records in another model when will prohibit me doing so. How can I best use the already defined relationships to check if delete will be successful? Potentially there could also be non-relationship reasons for not allowing a delete.

Once I have determined my error messages how can I best store them and pass them on to the front-end? beforeDelete() only returns true or false but I of course need to provide user with friendly error messages saying WHY the record can't be deleted...

Relationship already defined is for example:

public function getPhonenumbers() 
 return $this->hasMany(Phonenumber::class, ['ph_contactID' => 'contactID']);

From the answers of @vishuB and @rob006 I got ideas for coming up with my own solution which I think will be superior as I can provide multiple error messages, it can be used in an API as well, and it doesn't rely on try/catching exceptions:

public function beforeDelete() 
 if (!parent::beforeDelete()) 
 $this->addError('contactID', 'For some unknown reason we could not delete this record.');
 

 if (!empty($this->phonenumbers)) 
 $this->addError('contactID', 'Contact is linked to a used phone number and cannot be deleted.');
 

 if ($some_other_validation_fails) 
 $this->addError('contactID', 'Contact cannot be deleted because it is more than two months old.');
 

 return ($this->hasErrors() ? false : true);

Then in my action I do this:

$contact = Contact::findOne($contactID);
if (!$contact->delete()) 
 return $contact->getErrors(); //or use flash messages and redirect to page if you prefer

return true;

You can throw exception in beforeDelete() with error message, and catch it in controller.

public function beforeDelete() 
 if ($this->getPhonenumbers()->exist()) 
 throw new DeleteFailException('Records with phone numbers cannot be deleted.');
 

 return parent::beforeDelete();

And in controller action:

try 
 $model->delete();
 catch (DeleteFailException $esception) 
 Yii::$app->session->setFlash('error', $exception->getMessage());