Re: [Design] Should accessors throw exception ?

From:

"Ron AF Greve" <ron@localhost>

Newsgroups:

comp.lang.c++

Date:

Fri, 12 Sep 2008 23:26:22 +0200

Message-ID:

<48cade74$0$196$e4fe514c@news.xs4all.nl>

Hi,

I think returning a special value like end() or 0 for a pointer is the best
solution.

I think exception should only be used when something exceptional occurs, for
instance you expect a conifiguration file is there yet when you try to open
it it is missing or you try to access a database but the DBA took it down
for maintenance. This way you (or the user of your library) can catch those
thiings somewhere 'high up' in the code knowing that everything in between
is released and handled nicely and continue (maybe waiting a few minutes and
try again.

And indeed a find/get combination is more work. Also with the end() you make
it work the same as the STL.

Regards, Ron AF Greve

http://www.InformationSuperHighway.eu

"mathieu" <mathieu.malaterre@gmail.com> wrote in message
news:32642e01-cd96-49fc-9c22-5753d083ba5a@k13g2000hse.googlegroups.com...

Hi there,

I'd like to know if there is a general answer to the following
question: when making a public interface that access a container
should the function throw an exception when the element is not found ?
Otherwise I need two functions: a Find and a Get function which put
the burden on the application programmer to always call Find before
Get.
The other alternative would be to return some kind of sentinel (like
std::set<>::end() )...

Comments ?

Thanks
-Mathieu

eg.

#include <map>
#include <string.h>

struct Phone { int P; };
struct Name { const char *N;
bool operator <(Name const &n) const { return strcmp(N,n.N) < 0; }
};
struct YellowPage
{
void Insert(Name const &n,Phone const &p)
{ I.insert( std::map<Name,Phone>::value_type(n,p) ); }
bool Find(Name const & n) { return I.find(n) != I.end(); }
Phone const &Get(Name const&n) { return I.find(n)->second; }
private:
std::map<Name,Phone> I;
};