Re: Descriptive exceptions
On Feb 22, 1:31 am, "Alf P. Steinbach" <a...@start.no> wrote:
* Eugene Gershnik:
Alf P. Steinbach wrote:
* Eugene Gershnik:
1) [log as soon as possible] "if you can" - you never can
since you don't know whether the caling code wants you to log
Why shouldn't one know that? It's easy to arrange.
Possible but not easy and it heavily contradicts the KISS principle.
Some ways to do communicate level or details of logging to code that you
call:
* The logging is done via a logger object that the calling code
supplies at module initialization; the level of logging can be set
dynamically via that object.
* The called code resides in template classes that are specialized
with a logging policy; the level of logging is set statically, but
can be different for different specializations.
* There is a singleton that can be configured dynamically with what
what to log or otherwise, used via RAII objects declared in the
calling code.
What's not easy?
All of the above. ;-) First and third have no idea about caller wishes
so they don't work if the caller doesn't want you to log. The second
makes the decision on per-type basis rather than per-call.
And they are complicated to set up and complicate your library. As I
said elsewhere do you know of many libraries that do any of these?
In contrast, with logging in catch clauses all over the system, the
level or details of logging are hardwired in numerous places.
They are part of application logic and are hardwired just like the
rest of your application logic.
catch(my_exception & ex)
{
if (ex.code() == my_exception::first_bad_thing)
{
//we don't care about first bad thing
return;
}
else if (ex.code() == my_exception::second_bad_thing)
{
//log it and retry
Log(ex);
retry = true;
}
else
{
//we don't know how to handle this
throw;
}
}
You can see the whole algorithm above which clearly spells out when
you want to log, when you don't and when you leave the decision to
somebody above.
--
Eugene
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