On 2012-02-20 19:42, H. S. Teoh wrote:
On Mon, Feb 20, 2012 at 01:23:04PM -0500, Jonathan M Davis wrote:
On Monday, February 20, 2012 11:57:07 Andrei Alexandrescu wrote:
[...]
Exactly. I don't see how a disagreement follows from here. So isn't
it reasonable to design the exception such that it can offer
information pertaining to what went wrong, in a uniform manner?
[...]
I don't see how you could possibly make that uniform. It's very
non-uniform by its very nature. The handling _needs_ to be
non-uniform.
I think there's a misunderstanding here. What Andrei is trying to
achieve is something like this:
class Exception : Error {
Variant[string] data;
string formatMsg(LocaleInfo li) {
return formatLocale(li, msg, data);
}
}
class GetOptException : Exception {
this() {
data["..."] = ...;
...
}
}
I contend that using Variant here is not necessary. You can easily do
this instead:
class Exception : Error {
string formatMsg(LocaleInfo li) {
auto members = typeid(this).getMembers(null);
string msg;
foreach (member; members) {
if (member.name.startsWith("info")) {
... //format this field
}
}
return msg;
}
}
class GetOptException : Exception {
string infoOption; // this gets picked up by formatMsg
int internalData; // this is ignored
// No need to declare anything else except ctor to set
// the above fields.
}
This allows for a much cleaner, type-checked access to infoOption,
should the catching code know how to deal with GetOptException
specifically.
T
Currently getMembers doesn't work and if I recall correctly it's not
possible to get the value out of what getMembers returns. But that might
just be considered implementation issues.
--
/Jacob Carlborg
