Throwable class design

[rumbu]

On Wednesday, 30 January 2013 at 07:01:56 UTC, H. S. Teoh wrote:

> Not true. I use this idiom a lot: a lower level function throws 
> an error
> message (e.g., integer format error), and a catch-block halfway 
> up the
> call-chain modifies .msg to include contextual information 
> (e.g.,
> filename, line number) and rethrows the exception, so that at 
> the top
> level the error message contains both context information and 
> the
> low-level error message.
>
>
> T

I thought exceptions are meant to be catched, not rethrown.

If you are the developper of an end user solution, you'll catch 
the exception and you will display a message some way with the 
details that you need, or, better, you will silently drop the 
exception taking the necessary actions to resolve the cause. 
Throwing exceptions in the user's face is not so friendly.

If you are a library developper, you'll catch the exception and 
you will rethrow *another* exception wrapping the original 
exception in the next field through the constructor. Target 
developpers of your library have no interest in your detailed 
message, but in the *type* of the exception thrown. Their program 
flow cannot interpret messages.