Propagating errors from model to presenter

miska

Hi,

I'm new and I'm struggling a little how to propagate errors from model where they occur – data validation, database connections, fetches and stuff to a presentation layer. I can drop model and do everything in presenter or I can pass the presenter object to model which is only slightly better. What is the correct way to handle this? Would expect some kind of exceptions, but can't find anything relevant anywhere.

Thanks for any pointers.

CZechBoY

Yes, I would throw some exceptions, catch them in presenter/component and do what you think is possible. The exception can very – product not found/product not accessible/session not accessible/cache not accessible/database not accessible/invalid sql…

miska

Is there some special Nette way of doing exception? Tried what seemed like php way throw new Exception('Something bad happened.'); but got Class 'App\Model\Exception' not found as a result. Probably some namespacing issue I don't understand.

miska

My bad, I see the problem now, missing \, should be throw new \Exception('Something bad happened.'); definitely tried it but as Tracy caught it and the error page seemed same at first glance didn't noticed it worked. Sorry for the confusion. So solved for me, now I can try playing with Exception types and such and error handling in general. Thanks!

Marek Bartoš

new Exception used in namespace Example resolves to Example\Exception. Absolute class name needs backslash prefix \Exception or use statement use Exception;
https://www.php.net/…mespaces.php

Toanir

As CZechBoY suggests, do use exceptions for exceptional situations – edge cases that don't make sense to be handled at the point of code. For example if you're designing a Model::getRow() service which communicates with DB and an error occurs, you can choose typically between these approaches:

catch possible exceptions in the Model::getRow() (, log it) and return null
do not catch the exception (ideally describe the throw behavior by phpDoc annotation) and catch it where it makes sense, usually a Presenter

As far as handling the exception is concerned, you might be interested in the catchExceptions parameter . In short, Tracy catches and displays exceptions while in debug mode but in production mode, they end up in the errorPresenter, where you can decide what to display to the user

jiri.pudil

Is there some special Nette way of doing exception?

Nope, there is not. However, there are some general good practices you can follow; this blog post is imo a particularly good resource on exceptions in PHP.