The Right Approach to Exceptions

[Robert Clipsham]

On 18/02/2012 23:13, Andrei Alexandrescu wrote:
> On 2/18/12 4:26 PM, Jonathan M Davis wrote (abridged):
> GetOptException
> FlagArgumentMissingException
> InvalidFlagArgumentException
> UnknownFlagException
> FileException
> FileNotFoundException
> NotFileException
> NotDirException
> AccessDeniedException
>
> I died inside a little.
>
> Andrei

Perhaps something like:

class PhobosException : Exception
{
     this(string _module, uint flags) { ... }
}

try
{
     doSomething();
}
catch(PhobosException e)
{
     // An exception was thrown by phobos
     if (e.moduleOf == "file") {
         // An exception was thrown by std.file
         if (e.flags & FileException.NotFound) {
             // File wasn't found
         }
     } else if (e.moduleOf == "stdio") {
         // An exception was thrown by std.stdio
     }
     // We only want to handle file and stdio exceptions, rethrow
     throw e;
}

Some pros/cons:
  * Catch-all for all phobos exceptions
  * No binary bloat from having lots of exception classes
  * Can still handle specific exceptions
  * e.flags isn't type-safe
  * It's not particularly pretty
  * Can only have up to 32 different "exceptions" in a module (64 if you 
make it a ulong)
  * It looks stupid if you come from an OOP language like java and 
you're used to having 5000 catch blocks
  * No need to decide on any exception hierarchy, just throw a 
PhobosException

-- 
Robert
http://octarineparrot.com/